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Sample records for c71 dot bien

  1. Les controverses du bien mourir

    OpenAIRE

    Clapasson, Dominique; Pott, Murielle

    2009-01-01

    Actuellement, la question des situations de fin de vie se pose en problème social. La dénonciation du tabou de la mort et de l’acharnement thérapeutique suscite des interrogations éthiques relatives à la souffrance des malades. Dès lors, le bien mourir devient une préoccupation qui touche chacun d’entre-nous. En Suisse, l’aspiration à une mort pacifiée se meut en deux modèles distincts de la gestion des situations de fin de vie : les soins palliatifs et l’assistance au suicide. En oppositi...

  2. Productos derivados sobre bienes de consumo

    OpenAIRE

    Francisco Venegas Martinez; Salvador Cruz Ake

    2010-01-01

    Este trabajo de investigacion desarrolla un modelo de equilibrio general con expectativas racionales en tiempo continuo util para la determinacion de precios de contratos forward, contratos futuros, bonos cupon cero y opciones europeas (de compra y venta) sobre bienes de consumo. Para ello, el modelo considera un individuo representativo en una economia con dos bienes, los cuales son producidos con tecnologias estocasticas. Por ultimo, el modelo propuesto permite examinar estrategias para obt...

  3. Productos derivados sobre bienes de consumo

    OpenAIRE

    Francisco Venegas Martínez; Salvador Cruz Ake

    2010-01-01

    Este trabajo de investigación desarrolla un modelo de equilibrio general con expectativas racionales en tiempo continuo útil para la determinación de precios de contratos forward , contratos futuros, bonos cupón cero y opciones europeas (de compra y venta) sobre bienes de consumo. Para ello, el modelo considera un individuo representativo en una economía con dos bienes, los cuales son producidos con tecnologías estocásticas. Por último, el modelo propuesto permite examinar estrategias para o...

  4. A two-directional synthesis of the C58-C71 fragment of palytoxin.

    Science.gov (United States)

    Hodgson, Robert; Nelson, Adam

    2004-02-01

    A two directional approach, in which asymmetric dihydroxylation and reduction reactions were used to control absolute configuration, was exploited in the preparation of a C(2)-symmetrical dipyranone. The homotopic dihydropyran (DHP) rings of this precursor were differentiated statistically using by a Prevost reaction and further functionalisation. A second Prevost reaction was used to functionalise the other DHP; global deprotection and peracetylation gave a protected version of the C(58)-C(71) fragment of palytoxin. Methods which might be of value in future synthetic work were developed for the stereoselective functionalisation of THP rings similar to those found in this fragment.

  5. Bien y principio en Platón. Bien et principe chez Platon

    OpenAIRE

    Ramón Cámara, Begoña

    2015-01-01

    La tesis doctoral Bien y principio en Platón (Universitat de València y Université Paris Ouest Nanterre La Défense), escrita por Begoña Ramón y dirigida por los Profesores Tomás Calvo y Francis Wolff, viene a cubrir una laguna en los estudios sobre la Idea del Bien en Platón. Y es que, aunque se ha escrito mucho sobre el Bien en Platón, esta cuestión de permanente interés no ha sido nunca estudiada de manera acertada y suficiente. El presente trabajo trata de aportar por primera vez una defin...

  6. Prospective du commerce physique de biens culturels

    OpenAIRE

    Moati, Philippe

    2015-01-01

    Le commerce physique de biens culturels se trouve pris sous les feux croisés de deux tendances lourdes. La révolution numérique a d’abord fait naître un nouveau circuit de distribution – le commerce électronique –, lequel a immédiatement trouvé dans le domaine culturel l’un de ses terrains de développement les plus actifs. Elle a ensuite rendu possible la dématérialisation des contenus culturels : des fichiers informatiques, délivrés de machine à machine, deviennent des concurrents directs de...

  7. Prospective du commerce physique de biens culturels

    OpenAIRE

    Moati, Philippe; Chantepie, Philippe

    2015-01-01

    Si le commerce physique des biens culturels reste le maillon économique central de l’économie de la création, quel est son avenir dans le contexte de la révolution numérique qui tend à déstructurer les filières par le double effet de la dématérialisation des contenus culturels et de la migration d’une partie de l’offre et des transactions dans l’univers numérique ? L’exercice prospectif à court terme (horizon 2015) tente, à partir de l’identification des tendances lourdes et de l’observation ...

  8. El arte de vivir bien y dignamente

    Directory of Open Access Journals (Sweden)

    Aguinaga Benítez Oscar William

    1997-11-01

    Full Text Available

    Por tradición y a diferencia de otras culturas, nos han enseñado en la casa, escuela o colegio y mucho más en el trabajo a buscar amor, prosperidad, salud, felicidad y satisfacción en el exterior y jamás se nos ha hecho ver, ni se nos ha inculcado que la mayor riqueza está en el interior de cada uno de nosotros. Bien dice el doctor Dyer "se nos ha condicionado para creer que recibimos la gracia de la vida" y no para que disfrutemos de la inmortalidad de nuestro yo espiritual, se niega la opción de estar siempre acompañado de una energía que para muchos es lo divino y para otros es la conciencia.

  9. Electronic Structures and Optical Properties of Phenyl C71 Butyric Acid Methyl Esters

    Directory of Open Access Journals (Sweden)

    Cai-Rong Zhang

    2013-01-01

    Full Text Available Phenyl C71 butyric acid methyl ester (PC71BM has been adopted as electron acceptor materials in bulk heterojunction solar cells with relatively higher power conversion efficiency. The understanding of the mechanism and performance for the devices based upon PC71BM requires the information of conformations, electronic structures, optical properties, and so forth. Here, the geometries, IR and Raman, electronic structures, polarizabilities, and hyperpolarizabilities of PC71BM isomers are studied by using density functional theory (DFT; the absorption and excitation properties are investigated via time-dependent DFT with B3LYP, PBE0, and CAM-B3LYP functionals. The calculated results show that [6,6]PC71BM is more stable than [5,6]PC71BM due to the lower total energy. The vibrational modes of the isomers at IR and Raman peaks are quite similar. As to absorption properties, CAM-B3LYP functional is the suitable functional for describing the excitations of PC71BM because the calculated results with CAM-B3LYP functional agree well with that of the experiment. The analysis of transition configurations and molecular orbitals demonstrated that the transitions at the absorption maxima in UV/Vis region are localized π-π* transitions in fullerenes cages. Furthermore, the larger isotropic polarizability of PC71BM indicates that the response of PC71BM to applied external electric field is stronger than that of PC61BM, and therefore resulting into better nonlinear optical properties.

  10. Comparative-Analysis of Gene-Sequences Encoding Ammonia Monooxygenase of Nitrosospira Sp Ahb1 and Nitrosolobus- Multiformis C-71

    NARCIS (Netherlands)

    Rotthauwe, J.H.; De Boer, W.; Liesack, W.

    1995-01-01

    DNA encoding ammonia monooxygenase from two phylogenetically related autotrophic nitrifying bacteria, Nitrosospira sp. AHB1 and Nitrosolobus multiformis C-71, was amplified by PCR, The resulting products were cloned into the vector pCR-Script, A continuous region of DNA of about 1.5 kb for strain AH

  11. De la naturaleza del bien: contra los maniqueos

    OpenAIRE

    Agustin, Aurelio,, Santo, Obispo de Hipona

    2012-01-01

    El sumo bien, al cual no hay nada superior, es Dios; y por esto es un bien inmutable, realmente eterno e inmortal. Todos los otros bienes no son sino por él ; pero no de él. En efecto, lo que es de él, es lo que él mismo es; pero las cosas hechas por él, no son lo que es él mismo. Y por esto, si solo el es inmutable, todas las cosas que hizo, ya que las hizo de la nada, son mudables. En efecto, tan omnipotente es, que puede aún de la nada, es decir, de lo que absolutamente no es, hacer cosas ...

  12. Propriété, biens publics mondiaux, bien(s commun(s : Une lecture des concepts économiques

    Directory of Open Access Journals (Sweden)

    Jérôme Ballet

    2008-03-01

    Full Text Available La notion de bien public mondial s’est développée ces dernières années. Elle renvoie à un dépassement ambigu de la notion usuelle dans la théorie économique de bien public. A cette occasion elle ouvre le débat sur l’équité en complément de l’efficience. De ce fait, la confrontation de cette nouvelle notion avec l’analyse de l’efficience des régimes de propriété s’impose. Par ailleurs, la confrontation avec la notion de bien commun, notion elle aussi en développement, éclaire l’enjeu autour de l’équité.Property, Global Public Goods, Common Good(s : A Lecture. The concept of global public good emerged these last years. It proposes, in an ambiguous way, to go beyond the usual concept of public good. Then, added to usual questions on efficiency, the debate on fairness becomes a stake. Confrontation with analysis on property rights command attention, Furthermore, confrontation with the concept of common good, also a developing concept, highlight stake around fairness.

  13. La place de l’évaluation des biens environnementaux dans la décision publique

    OpenAIRE

    Point, Patrick

    2007-01-01

    Dans les économies d’aujourd’hui, la plupart des biens et des services se voient dotés d’un prix. Ce prix agit comme un signal permettant d’orienter et de coordonner les comportements des consommateurs et des producteurs. Les ressources naturelles qui sont des dons de nature n’ont pas, pour nombre d’entre elles, un repère de prix qui leur soit attaché. Ceci crée une responsabilité spéciale pour les pouvoirs publics. Il est en effet nécessaire d’identifier les services rendus par les actifs na...

  14. Bien común y ética pública: Alcances y límites del concepto tradicional de bien común

    OpenAIRE

    Dorando J. Michelini

    2007-01-01

    Con el concepto de bien común se ha hecho referencia, a través de la historia, a aquellos bienes materiales e inmateriales que no se circunscriben a una persona sino que remiten a todos y cada uno de los miembros de la sociedad. Entre esos bienes suelen contarse elementos básicos para la supervivencia humana biológica, como el aire y el agua, pero también el derecho a participar en el usufructo de los bienes de la cultura. En algunos casos, el bien común es equiparado al bienestar general; en...

  15. Bien común, derecho social y ciencias sociales

    OpenAIRE

    Zamagni, Stefano

    2014-01-01

    Stefano Zamagni, Catedrático de Economía Política de la Universidad de Bolonia. Bien común, Derecho Social y Ciencias Sociales. Conferencia en la Universidad de Málaga el 4 de noviembre de 2014. Facultad de Derecho. Departamento de Derecho del Trabajo y de la Seguridad Social. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Stefano Zamagni, profesor de Economía Política en la Universidad de Bolonia y en la John Hopkins University, es uno de los princi...

  16. El mercado de bienes ilegales: el caso de la droga

    Directory of Open Access Journals (Sweden)

    Becker , Gary S.

    2006-12-01

    Full Text Available Este artículo examina los costos de reducir el consumo de un bien declarando ilegal su producción y castigando a los productores ilegales. Las drogas son el ejemplo más destacado. Cuanto más inelástica es la demanda o la oferta, mayor es el incremento del costo social de reducir la producción con mayor represión. Así, el gasto público óptimo de capturar y condenar a los proveedores ilegales no sólo depende de la diferencia entre los valores social y privado del consumo sino también de las elasticidades. Cuando la demanda y la oferta no son muy elásticas, no paga hacer cumplir la prohibición a menos que el valor social sea negativo. También muestra que un impuesto monetario reduce la producción e incrementa el precio más que la represión óptima del bien si fuera ilegal, aunque algunos productores vayan a la clandestinidad para evadir el impuesto monetario. Los impuestos al consumo y las restricciones a las cantidades no son equivalentes cuando la represión tiene costos

  17. Le commerce électronique de biens culturels : contributions empiriques

    OpenAIRE

    Eang, Bora

    2012-01-01

    Cette thèse se présente sous la forme d’un volume de 134 pages composé de 5 articles de recherche. La thèse est une contribution empirique à la littérature qui s’est développée depuis le début des années 2000 sur les bouleversements introduits par Internet sur le commerce des biens culturels. Elle examine plus particulièrement un ensemble de questions portant sur la complémentarité ou la substitution des canaux de distribution, physiques et virtuels, l’effet de « Longue Traîne » et la dispers...

  18. Los bienes comunes intangibles en el capitalismo cognitivo.

    Directory of Open Access Journals (Sweden)

    Álvaro Ramis Olivos

    2014-10-01

    Full Text Available Normal 0 21 false false false MicrosoftInternetExplorer4 Este texto analizará críticamente la actual fase económica para mostrar la importancia de los bienes comunes intangibles. Sondea la tesis de un nuevo modo de producción «en ciernes», basado en la gestión colaborativa. Analiza los intangibles de acuerdo a su calidad y carácter. Compara los sistemas de patentes y derechos de propiedad intelectual que permiten su apropiación y las resistencias a su «comoditización» desde el software libre y las propuestas de flexibilización de derechos de autor. Advierte sobre el «fetichismo tecnológico» y propone un marco mínimo de discernimiento en dilemas vinculados a estas materias. /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Tabla normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;}

  19. Ciberciudadanía, cultura y bienes públicos

    Directory of Open Access Journals (Sweden)

    Álvarez, J. Francisco

    2009-06-01

    Full Text Available Net society is provoking dramatic changes in several aspects of our daily life as cultural traits, business and the more disparages spheres of privacy and social life. We must attend both to freedom of access and to new services generation because of the peculiar form public goods are raising in the Net. To supersede individual capability limitations and to diffuse digital and cultural gaps, electronic government could be a cultural decisive tool in this phase of cibersociety enhancement. Technologies enhanced the human capabilities, as well as with the social actions and its framework, including cultural production and management. Technologies are also transforming the generation, reproduction and transmission of (social knowledge.La sociedad red transforma la vida cotidiana, las diversas manifestaciones culturales, los negocios, las esferas más diversas de la vida privada y social. La forma en que se generan los bienes públicos en la red exige una preocupación explícita por la libertad de acceso y la generación de nuevos servicios, que ayuden a superar limitaciones de los individuos y faciliten desdibujar las diversas brechas digitales y ciberculturales. El gobierno electrónico resulta culturalmente decisivo en esta fase de expansión de la cibersociedad. Las tecnologías amplían las capacidades humanas, expanden el espacio y las formas de acción social, incluidas la producción y gestión cultural. También producen cambios en las formas de generación, reproducción y transmisión del conocimiento (social.

  20. Economía institucional de un bien mayor

    Directory of Open Access Journals (Sweden)

    Óscar A. Alfonso Roa

    2007-12-01

    Full Text Available La provisión de los servicios de acueducto y alcantarillado en Colombia ha sido sometida, desde 1994, a una terapia consistente en la promoción de un modelo empresarial que se abre paso a costa de la estigmatización del municipio como mal prestador y como asignador ineficiente de unos recursos escasos. a quince años de operación del modelo empresarial y en desarrollo del Acto Legislativo 04 de 2007, el Gobierno nacional ha introducido otra reforma, en esta oportunidad al Sistema General de Participaciones, esgrimiendo en la exposición de motivos los mismos argumentos de antaño, cuando en verdad mediante la prestación directa de los municipios sólo se provee de estos servicios a una porción minoritaria de la población urbana del país. En la primera parte se discute la noción del agua potable como bien mayor y en la segunda se presenta una breve síntesis de la evolución institucional de la provisión del agua potable en colombia. en la tercera parte se discuten algunos rasgos centrales del proceso de urbanización de la población colombiana a la que se sirve con el servicio de acueducto mientras que en la última se analiza la coyuntura reciente con énfasis en la crítica a la reforma introducida por el acto Legislativo 04 de 2007. este artículo propone otros puntos de vista para criticar, además de la reforma en curso, las fallas de un esquema de provisión cifrado en un enfoque empresarial sometido a una inocua regulación, que no logra conciliar los intereses de ampliación de las ganancias de las empresas de servicios públicos con las aspiraciones sociales en materia de universalización y calidad de los servicios de acueducto y alcantarillado.

  1. Bien común y ética pública: Alcances y límites del concepto tradicional de bien común

    Directory of Open Access Journals (Sweden)

    Dorando J. Michelini

    2007-12-01

    Full Text Available Con el concepto de bien común se ha hecho referencia, a través de la historia, a aquellos bienes materiales e inmateriales que no se circunscriben a una persona sino que remiten a todos y cada uno de los miembros de la sociedad. Entre esos bienes suelen contarse elementos básicos para la supervivencia humana biológica, como el aire y el agua, pero también el derecho a participar en el usufructo de los bienes de la cultura. En algunos casos, el bien común es equiparado al bienestar general; en otros, a la suma de intereses particulares o al beneficio de la mayoría, como cuando se busca el mayor bien para el mayor número posible de individuos. Más allá de las diversas interpretaciones, la promoción del bien común sigue siendo en la actualidad un objetivo clave del Estado en el ideario democrático y un tema recurrente de la ética pública. En lo que sigue, se reconstruye críticamente el concepto tradicional de bien común, haciendo especial referencia a las obras de Platón, Aristóteles y Santo Tomas, con el fin de sentar bases para una nueva comprensión de la idea de bien común en sociedades pluralistas y democráticas.With the concept of commom good reference has been made, along history, to those material and immaterial goods which are not circumscribed to a person, but remit to each and every member of society. Among those goods, basic elements for biological human survival, such as air and water, are usually included, but also the right to participate of the profits of cultural goods. In some cases, commom good has been made equivalent to common wellfare; in others, to the summation of particular interests or to the benefit of the majority. Beyond the diverse interpretations, the promotion of common good continues at present to be a key aim of State in the democratic ideary and a recurrent issue in public ethics. In what follows, the concept of traditional common good has been reconstructed, making special reference to the

  2. Bienes comunes, nuevos cercamientos y economía política popular

    OpenAIRE

    Lain Escandell, Bru

    2015-01-01

    Este artículo discute la creciente importancia que están adoptando los llamados bienes comunes en el ámbito de la creación cultural. Para ello se discuten críticamente dos importantes analogías que han emergido en los últimos años: la primera, entre los bienes comunes naturales y los digitales y la segunda, entre los viejos y los nuevos cercamientos digitales. El artículo demuestra que, si bien es cierto que ambas comparaciones deben abordarse con cautela, las similitudes entre ambas son nota...

  3. Bien écrire en affaires savoir rédiger pour être lu et convaincre

    CERN Document Server

    Berrou, Jean-Paul

    1991-01-01

    Ce qu'il faut savoir pour bien rédiger ses écrits professionnels au travers d'une démarche méthodique pour bien organiser sa pensée en vue d'écrire efficacement, de conseils et de techniques pour être compris à coup sûr et être lu jusqu'au bout avec intérêt. Agrémenté de nombreux exemples concrets.

  4. TRASMISIÓN DE BIENES Y REGISTRO DE LA PROPIEDAD EN ESPAÑA (SEGUNDA PARTE

    Directory of Open Access Journals (Sweden)

    Joaquín Sánchez Cebrián

    2009-01-01

    Full Text Available La circulación de los bienes en el tráfico jurídico por la voluntad de los particulares es un tema crucial que interesa, no sólo a las partes del contrato, sino, a todos en general, y, en particular, a los acreedores del transmitente o del adquirente y a los terceros adquirentes de derechos sobre el bien. En este trabajo se analizará el régimen de trasmisión de los bienes por negocio inter vivos en el Derecho español, dentro del marco europeo, y con particular referencia a la trasmisión inmobiliaria. España adopta un peculiar sistema de trasmisión de los bienes porque se establecen reglas genéricas cuya aplicación se da con independencia de la naturaleza mueble o inmueble del bien; pero a su lado se superponen otras que tratan de fijar los efectos de la publicidad registral inmobiliaria. La coordinación entre dichas reglas produce un original resultado, que puede constituir el punto de encuentro de los diversos sistemas registrales europeos.

  5. L’éducation, un bien commun très particulier

    OpenAIRE

    Proulx, Jean-Pierre

    2015-01-01

    Dans ce texte, le président du Conseil supérieur de l’éducation discute de celle-ci en tant que bien commun, mais également en tant que bien particulier. Il démontre l’importance du rôle de l’État en matière d’accessibilité à l’éducation. Ainsi, en pratique, seul l’État, en tant que responsable premier du bien commun et de la justice distributive, est capable d’assurer cette accessibilité à tous et en pleine égalité, grâce aux impôts et aux taxes qu’il perçoit des citoyens et des entreprises....

  6. Swift multi-wavelength observations of the high-redshift Blazar S5 0836+710 (4C 71.07)

    Science.gov (United States)

    Vercellone, Stefano; Romano, Patrizia; Raiteri, Claudia Maria; Acosta Pulido, Jose; Villata, Massimo; Carnerero Martin, Maria Isabel

    2016-04-01

    We present the preliminary results of a year-long Swift monitoring campaign of the high-redshift (z=2.172) flat-spectrum radio quasar (FSRQ) S5 0836+710 (4C 71.07). The campaign, based on one observation per month, 5 ks each observation, for 12 months, allowed us to investigate the synchrotron and nuclear emission contributions to the optical-UV frequency range of its spectral energy distribution and the X-ray spectral variations along a baseline of a year. We obtained a high-accuracy determination of UVOT magnitudes, an X-ray photon index with an uncertainty of the order of 5%, and well-sampled light curves both in the optical-UV and X-ray energy bands to study their possible modulations and correlations. Our study allowed us to exploit the unique Swift capabilities in terms of both simultaneous energy coverage and schedule flexibility. The Swift monitoring campaign was supported by observations by the GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT) Collaboration, which provided radio, near-infrared, and optical photometric data as well as optical polarimetry. Moreover, a spectroscopic monitoring was obtained at the William Herschel Telescope (WHT) and the Nordic Optical Telescope (NOT). All these observations will allow us to obtain a comprehensive picture of the jet as well as of the nuclear source emission.

  7. Los bienes prestados: Estrategias feudales de consolidación señorial

    OpenAIRE

    Jular Pérez-Alfaro, Cristina

    1999-01-01

    Este artículo analiza las operaciones denominadas prestimonia en los textos medievales: un tipo particular de cesión de bienes, principalmente de tierras, realizada en calidad de préstamo de por vida, por una autoridad señorial a otra entidad y sirviendo el usufructo de los bienes concedidos como pago de lo adquirido. Tema con cierta tradición historiográfica, se pretende ahora someterlo a un nuevo cuestionario, introducirlo en la conceptualización amplia de "lo prestado" y ver resultados con...

  8. bien reconocida

    Directory of Open Access Journals (Sweden)

    N. Prat

    2015-01-01

    Full Text Available En el año 2014 se conmemora el décimo aniversario de la muerte del Profesor Ramón Margalef. En este artículo se hace un repaso a las publicaciones realizadas por el Dr. Margalef, que llegan a un total de 563 trabajos. La temática dominante de los mismos es la ecología acuática, tanto marina como de agua dulce, y mayormente centrados en los estudios de plancton. Sus trabajos están sobre todo publicados en castellano, en catalán y, en menor medida en inglés, en casi 100 revistas diferentes de todo tipo (desde revistas divulgativas a científicas. Destacan por número los artículos publicados en las revistas “Investigación Pesquera” y “Publicaciones del Instituto de Biología Aplicada”, aunque numéricamente los capítulos de libros y las actas de congresos dominan sus trabajos. De todos estos trabajos, 383 se encuentran citados en la “Web of Science” con un promedio cercano a las 100 citas por año, destacando su trabajo de 1978 sobre las formas de vida del fitoplancton, que sigue siendo muy citado (más de 50 citas por año y con tendencia incluso a crecer en el tiempo. Es destacable el poco conocimiento que se tiene de sus libros (con excepción del primero que publicó en inglés titulado “Perspectives in Ecological Theory”, de 1968. A pesar del gran reconocimiento internacional que tuvo Margalef en vida, hoy en día parece que su obra es en gran parte desconocida por los ecólogos del siglo XXI. Su nombre ha desaparecido de los libros de texto de ecología y una de sus grandes aportaciones a la ecología moderna (introducir la teoría de la información en Ecología y el índice de Shannon-Weaver como medida de diversidad no aparece en los manuales de ecología.

  9. Repensando los bienes comunes: análisis socio-técnico sobre la construcción y regulación de los bienes comunes

    Directory of Open Access Journals (Sweden)

    Ariel Vercelli

    2008-09-01

    Full Text Available El presente artículo analiza los bienes comunes desde una perspectiva socio-técnica. Puntualmente, invita a repensarlos en función de algunos cambios tecnológicos recientes. A partir de esta perspectiva es posible observar cómo los bienes comunes son parte de un proceso continuo de luchas, negociaciones y redefiniciones políticas entre diferentes grupos de actores. Analiza como estas luchas políticas son parte de un proceso de co-construcción entre el diseño tecnológico y las nuevas formas de regulación.This article discusses the commons ("common goods" from a socio-technical view. Specifically, it invites us to rethink them in the light of some recent technological changes. From this perspective it is possible to see how the commons are part of a continuous process of struggles, negotiations and political re-definitions among different groups of players. Analyze how these political struggles are part of a process of co-construction between the design of technologies and new forms of regulation.

  10. Quantum dot spectroscopy

    DEFF Research Database (Denmark)

    Leosson, Kristjan

    1999-01-01

    Semiconductor quantum dots ("solid state atoms") are promising candidates for quantum computers and future electronic and optoelectronic devices. Quantum dots are zero-dimensional electronic systems and therefore have discrete energy levels, similar to atoms or molecules. The size distribution...

  11. Les dépenses Publiques : quel optimum pour un bien être social ?

    OpenAIRE

    Benloulou, Salim-badreddine

    2014-01-01

    L’objectif de ce travail étant de présenter un cadre d’analyse montrant la relation éventuellement existante entre les dépenses publiques et le bien-être social en Algérie. La présente étude comporte un cadre théorique ayant trait à la définition des concepts et outils de calculs et d’évaluation de l’indice du bien-être rapporté à l’Algérie. Globalement, les résultats montrent qu’il existe un lien positif et significatif entre l’augmentation des dépenses publiques et le b...

  12. La publicidad de bien público y la educación sexual en Cuba

    OpenAIRE

    Hernández Alfonso, Eduardo Alejandro; Paz Enrique, Luis Ernesto

    2016-01-01

    La prevención es una premisa de la educación en salud cubana. Se plantean como objetivos del estudio identificar las características del diseño gráfico cubano para la prevención de las ITS y diseñar una propuesta de bien público basado en nuevos criterios estéticos. El estudio clasifica como investigación aplicada. Se utilizan métodos en los niveles teóricos y empíricos para la recogida de información. La investigación analiza las campañas de bien público orientadas a la prevención de las inf...

  13. Usurpaciones de bienes concejiles en Salamanca durante el Reinado de los Reyes Católicos

    Directory of Open Access Journals (Sweden)

    Clara Isabel LÓPEZ BENITO

    2009-12-01

    Full Text Available La realidad económica-social castellana de la Edad Moderna se caracterizó por ser fundamentalmente agraria. Un porcentaje muy elevado de la población activa del Reino trabajaba en el campo, y de él procedía el grueso de las rentas que sustentaban la vida nacional. En la mayoría de los municipios castellanos, junto a las posesiones particulares y junto a aquellas otras que teóricamente pertenecían al rey, existieron las llamadas "tierras concejiles" (o "comunitarias" como prefieren otros autores. Dentro de ellas había que distinguir los "bienes comunales", libremente aprovechados por los vecinos del término municipal, y los "bienes de propios", que el concejo alquilaba a particulares a cambio de una renta que resolvía diversos gastos de la Administración local.

  14. Santé et biens communs : un regard de juriste.

    Directory of Open Access Journals (Sweden)

    Isabelle Moine-Dupuis

    2010-11-01

    Full Text Available La santé constitue un domaine dans lequel les notions de bien commun ou de bien public mondial sont particulièrement pertinentes. Il faut cependant préciser de quels biens il est question. A titre d’exemple, le droit français comporte des notions susceptibles de qualifier le droit aux soins (comme droit inaliénable, ou le médicament, objet de propriété intellectuelle comme de propriété « traditionnelle ». Un droit international des biens de santé peut de la même manière être fondé sur un droit d’usage de chacun sur la molécule qui est la même dans le médicament générique et celui de marque. Une procédure d’accès équivalent aux produits, brevetés ou non, pourrait être mise en œuvre par principe dès la découverte, afin de parvenir rapidement à des prix équitables.Health is a field particularly suitable for notions as commons or public goods. It is necessary however to know which goods may be concerned. For instance, French lawyers use concepts which can be used in order to qualify right to care (as an inalienable right, or medicine as an object of intellectual property as well as “traditional” one. An international law for health goods could be also based on a right of use for each person on the molecule which is the same in the generic drug or in the patented one. A process of “equivalent access” to licensed or free products could be initiated, from the discovery itself to the use, in order to obtain rapidly fair prices.

  15. EL PATRIMONIO COMO REPRESENTACIÓN COLECTIVA: LA INTANGIBILIDAD DE LOS BIENES CULTURALES

    Directory of Open Access Journals (Sweden)

    Javier Marcos Ar\\u00E9valo

    2012-01-01

    Full Text Available Enfocado desde la perspectiva de la antropología social, el artículo se estructura en torno a los conceptos de tradición, bienes culturales intangibles y representación de la memoria social. Desde planteamientos críticos el trabajo revisa textos fundamentales y analiza y valora los documentos que sobre patrimonio inmaterial ha hecho público la UNESCO en los últimos quince años.

  16. Sobre el desarrollo de la teoría de los bienes públicos locales

    Directory of Open Access Journals (Sweden)

    Miltón Samuel Camelo

    2015-12-01

    Full Text Available La teoría de los bienes públicos locales toma forma desde la concepciónde la hipótesis de Tiebout, que es el primer planteamiento que tuvo en cuentala dimensión espacial de los bienes públicos, y constituye un mecanismo para la revelación de las preferencias sobre este tipo de bienes. Este trabajo desarrolla la analogía entre el modelo de Tiebout y el modelo neoclásico como una herramienta de dirección del trabajo y no como fin mismo pues, de lo contrario, puede terminar en una discusión ideológica que no es pertinente. Se examina el desarrollo de la teoría a través de la revisión de tópicos relevantes y aportes que han enriquecido y complementado el modelo de Tiebout; y, finalmente, describe elementos esenciales que debe incorporar la teoría para que tenga un mayor poder explicativo.

  17. OF THE COMMON GOOD TO THE COMMON GOOD OF HUMANITY. DE LOS BIENES COMUNES AL BIEN COMÚN DE LA HUMANIDAD.

    Directory of Open Access Journals (Sweden)

    François Houtart.

    2014-06-01

    éndum sobre el agua (uno de los bienes comunes en Italia, la Fundación Rosa Luxemburgo tomó la decisión de organizar una Conferencia sobre el concepto del Bien Común de la Humanidad, para promover una reflexión sobre los vínculos entre las dos nociones y de integrar las reivindicaciones y las luchas sociales para un cambio de sociedad, escenario en el que se enmarca éste artículo.

  18. Los Bienes Destinados al Uso General: Tratamiento Contable en Diferentes Administraciones Locales Europeas

    Directory of Open Access Journals (Sweden)

    María Teresa Balaguer Coll

    2001-06-01

    Full Text Available Como respuesta a la necesidad de una mayor información para la gestión, los sistemas contables públicos han sido sometidos a un proceso general de reforma, especialmente en la administración local. Estas reformas afectan, entre otros, al tratamiento contable de los activos fijos. Dada la especial naturaleza que poseen algunos de estos activos, como es el caso de los bienes destinados a uso general, este artículo tiene por objeto analizar la problemática contable que tales bienes originan, mostrando diferentes posturas académicas y las prácticas contables de las entidades locales en diferentes países europeos. En general, se aprecia una clara tendencia a la presentación de mayor información sobre el activo fijo en los estados financieros, siendo el criterio de valoración más utilizado el coste histórico. Palabras clave: bienes de uso general, contabilidad pública, entidades locales europeas. ABSTRACT In response to the need for better management information, pubic sector accounting systems have been subjected to a general reform process, especially in local government. These reforms cover, among other things, accounting for capital assets. Given the special nature of some of these assets, such as community assets, this article aims to analyse the problematic roots of accounting, examining different academic positions as well as the accounting rules and practices of local authorities in different European countries. In general, there appears to be a clear tendency to present more information on capital assets in financial statements, with historic cost being the most utilised valuation criteria.

  19. Determinantes de los precios internacionales de los bienes básicos

    OpenAIRE

    Carolina Arteaga; Joan Granados; Jair Ojeda

    2012-01-01

    En este trabajo se analiza la respuesta dinámica de los precios de los bienes básicos más relevantes para la evolución de la inflación en Colombia ante choques en un conjunto de sus determinantes. El documento está basado en modelos VAR estructurales en los cuales los choques exógenos son identificados mediante restricciones a los efectos contemporáneos entre las variables del sistema. Para la estimación se utilizan datos trimestrales para el periodo 1980q1 a 2010q3. De acuerdo con los result...

  20. Le Bonheur national brut et les indicateurs de richesse: bien-être et animation socioculturelle

    OpenAIRE

    Carron, Florine; Délez, Marie-­‐Luce

    2016-01-01

    L’objectif principal de ce travail de Bachelor a été d’identifier puis d’analyser les valeurs communes en lien avec le «bien-être» et le «bonheur» dans les systèmes politiques de gouvernance dans le monde. En parallèle, une analyse sur les fonctions, les valeurs et les objectifs de l’animation socioculturelle a été réalisée afin de mieux comprendre comment les professionnels de la branche peuvent contribuer au Bonheur national brut au travers de leurs différents rôles et fonctions....

  1. Adolescentes intelectualmente bien dotados. Una investigación en la provincia de Toledo.

    OpenAIRE

    Hume Figueroa, Miriam; Sánchez Núñez, María Trinidad

    2004-01-01

    Este artículo sintetiza los resultados de una investigación sobre identificación de alumnos intelectualmente bien dotados de 1º de E.S.O. en la provincia de Toledo, que comienza en mayo de 1993 y que todavía está en curso. Mediante el método de filtrado o screening aplicamos la prueba Matrices Progresivas de Raven a casi 6.000 alumnos del curso mencionado. Escogimos la franja de alumnos que se situaba muy por encima de la media, según los resultados de dicha prueba, para realizar un estudio m...

  2. La protección transfronteriza de los bienes inmateriales en el comercio internacional

    OpenAIRE

    De Miguel Asensio, Pedro Alberto

    2008-01-01

    RESUMEN Pese a los logros de los convenios internacionales en materia de propiedad industrial e intelectual, no se ha superado el modelo basado en la territorialidad. La creciente complejidad de las actividades de explotación e infracción de los bienes inmateriales y su alcance típicamente internacional han contribuido a acentuar el debate sobre la revisión de su tratamiento en los sistemas de Derecho internacional privado, al tiempo que han dado lugar a un interés por desarrollar estánda...

  3. El reconocimiento de los bienes de dominio público: El caso de los municipios portugueses

    Directory of Open Access Journals (Sweden)

    Susana Catarino Rua

    2016-02-01

    Full Text Available Objeto: Este trabajo tiene por objetivos analizar el mencionado en el POCAL (1999, en las NICSP del IPSASB y en diversas opiniones doctrinales con respecto al reconocimiento de los bienes de dominio público (BDP, así como verificar si existen problemas inherentes al reconocimiento de los BDP en Portugal, superables con la adopción de las NICSP. Diseño/metodología/Enfoque: Para este estudio, fue efectuada una revisión de literatura, de la posición del POCAL (1999, de las NICSP del IPSASB, y de la perspectiva doctrinal, con respecto al reconocimiento de los bienes de dominio público. Además, se realizó un estudio de la evolución de los valores de los bienes de dominio público, de los años 2006 a 2013, del total de los 308 municipios portugueses, para concluir acerca de la existencia de dificultades en el reconocimiento de estos activos y de la necesidad de adoptar los normativos internacionales. Aportaciones y Resultados: En algunos municipios portugueses, el proceso de inventario aún no está concluido, existiendo dificultades con respecto al reconocimiento de los BDP. Dichas dificultades resultan de que el POCAL (1999 no presenta los requisitos para el reconocimiento de los activos; problema superado en la NICSP nº 17 del IPSASB (2006b, que refiere esos requisitos. Adoptar un nuevo Sistema de Normalización Contable aplicable a la Administración Pública (SNC-AP, basado en las NICSP, puede ser la solución para dichas cuestiones, introduciendo criterios a considerar en el reconocimiento de los activos, que aseguren la comparabilidad de la información y de los valores del patrimonio de los municipios portugueses. Limitaciones: La inexistencia de criterios de reconocimiento a seguir por los municipios trae limitaciones al nivel de la comparabilidad de los valores de los diferentes componentes del activo presentados por los varios municipios. Valor añadido: Este trabajo nos enseña que, en Portugal, aún existen problemas con

  4. Restauración del capital natural: sin reservas no hay bienes ni servicios

    OpenAIRE

    Aronson, James; Renison, Daniel; Rangel Churio, Jesús Orlando; Levy Tacher, Samuel; Ovalle Molina, Carlos; Pozo Lira, Alejandro del

    2007-01-01

    Una de las ideas más innovadoras y atractivas que se están acuñando en la actualidad está relacionada con la necesidad que tiene la humanidad de preservar y manejar los recursos naturales - o capital natural - remanente e invertir en la restauración del capital natural (RCN) degradado para reincorporarlo a la cadena de bienes y servicios que la sociedad requiere. En este artículo, presentamos definiciones y conceptos básicos, para mostrar como la RCN es un enfoque más amplio en re...

  5. Restauración del Capital Natural: sin reservas no hay bienes ni servicios

    OpenAIRE

    Aronson, J.; D. Renison; Rangel-Ch, J. O.; S. Levy-Tacher; Ovalle, C.; del Pozo, A.

    2007-01-01

    Una de las ideas más innovadoras y atractivas que se están acuñando en la actualidad está relacionada con la necesidad que tiene la humanidad de preservar y manejar los recursos naturales o capital natural - remanente e invertir en la restauración del capital natural (RCN) degradado para reincorporarlo a la cadena de bienes y servicios que la sociedad requiere. En este artículo, presentamos definiciones y conceptos básicos, para mostrar como la RCN es un enfoque más amplio en relación al pr...

  6. Die biene und ihre produkte in der kunst und im alltagsleben (Fruhchristliche und byzantinische Zeit

    Directory of Open Access Journals (Sweden)

    Liveri Angeliki

    2010-01-01

    Full Text Available Die vorliegende Arbeit ist in zwei Teile geteilt: den kunst- und kulturhistorischen Teil. Im ersten Teil werden Darstellungen uber Bienen Bienenzucht, Honig und Wachs seit der fruhchristlichen bis zur spatbyzantinischen Zeit vorgefuhrt. Daher ist es als Beitrag in der "Ikonographie" der Biene wahrend dieser Zeit zu verstehen. Im kulturhistorischen Teil werden Informationen uber die Bienenzucht, den Handel mit Honig und Wachs sowie ihre vielfaltige Anwendung von der byzantinischen Gesellschaft an Hand der primaren Quellen, des Standes der Forschung und der archaologischen Funden erwahnt. Damit ist erwunscht ein moglichst gutes Bild der byzantinischen Bienenzucht wieder zu geben und die Nutzung der Bienenprodukte in Byzanz anschaulich zu machen.

  7. Memoria sobre la Red de Estudio y Enseñanza Interdisciplinar del Gobierno del Bien Común

    OpenAIRE

    Ortiz García, Mercedes; Garay Montañez, Nilda; Gómez Calvo, Verónica; Hidalgo Moratal, Moisés; Carmen PASTOR SEMPERE; Romero-Tarín, Adela

    2015-01-01

    El presente trabajo en red docente ha servido para cuestionar y proponer la reformulación de la enseñanza y la investigación universitaria a partir del “gobierno del bien común”. Desde la Red se ha pretendido reformular el concepto de “bien público” como “bien común” para recalcar el uso común de dichos bienes y la necesidad de su conservación en buen estado para asegurar dicho uso, y evitar las peligrosas “privatizaciones encubiertas”. De ahí que nuestra Red a través de sus distintas discipl...

  8. 富勒烯衍生物苯基C71-丁酸甲酯的结构和电学性质第一性原理研究%First principles calculations of structure and the electronic properties of fullerene derivative phenyl-C71-butyric acid methyl ester

    Institute of Scientific and Technical Information of China (English)

    张竹霞; 赵彦亮; 闫新; 韩培德; 刘旭光; 郝玉英; 许并社

    2009-01-01

    Phenyl-C71-butyric acid methyl ester ([70]PCBM) clusters are investigated by using the B3LYP method with 6-31G(d) basis set. The optimized results indicate that the addition of PCBM into the [6,6]-junction produces a closed methanofullerene which is thermodynamically stable product; and the addition into the [5,6]-junction results in an enlarged fullerene (an open fulleroid) which is a kinetically controlled product. The first adiabatic electron affinity for [70]PCBM is similar to that for C70. The energy gaps of [70]PCBM are reduced compared with those of C70. PCBM derivatives and show increased level of the lowest unoccupied molecular orbital of fullerenes. From the natural charge populations, it is found that adding PCBM unit onto the C70 cages does not change the charge populations remarkably; attaching a PCBM has no effect on the electronic structures of C70. The results of theoretical calculation suggest that PCBM is not involved in the process of photoelectric conversion but it plays a key role in adjusting the level of HOMO-LUMO for increasing photoelectric conversion efficiencies.%使用B3LYP/6-31G(d)方法对有机太阳电池中作为电子受体材料的富勒烯衍生物苯基C71-丁酸甲酯([70]PCBM)的同分异构体进行了计算.PCBM与C70通过六元环和六元环共用的CC双键加成得到的产物是热力学控制产物;通过五元环和六元环共用的C-C键加成得到的产物则是动力学控制产物.[70]PCBM与C70的第一绝热电子亲和势很接近.PCBM对前线轨道贡献很小,[70]PCBM的最高占据分子轨道和最低未占据分子轨道(LUMO)的电子云主要分布在C70笼上.PCBM提升了C70的LUMO能级水平,有利于提高太阳电池的光电转换效率.自然布居分析表明,PCBM与C70之间没有发生显著的电荷转移.所有的性质研究表明,PCBM基团并不涉及电池光电转换过程,但在调整C70能级水平提高光电转换效率中发挥了重要作用.

  9. Restauración del Capital Natural: sin reservas no hay bienes ni servicios

    Directory of Open Access Journals (Sweden)

    J. Aronson

    2007-01-01

    Full Text Available Una de las ideas más innovadoras y atractivas que se están acuñando en la actualidad está relacionada con la necesidad que tiene la humanidad de preservar y manejar los recursos naturales o capital natural - remanente e invertir en la restauración del capital natural (RCN degradado para reincorporarlo a la cadena de bienes y servicios que la sociedad requiere. En este artículo, presentamos definiciones y conceptos básicos, para mostrar como la RCN es un enfoque más amplio en relación al propuesto en la restauración ecológica de ecosistemas naturales. Damos a conocer estudios de caso, como ejemplos del enfoque de la RCN, y su impacto sobre el suministro de bienes y servicios en Argentina, Colombia, México y Chile. Terminamos con una breve discusión y algunas recomendaciones para la investigación y el desarrollo de la RCN a nivel local, regional y global.

  10. Vite et bien 1 A1/A2 : méthode rapide pour adultes

    CERN Document Server

    Miquel, Claire

    2009-01-01

    Vite et bien s'adresse à des adultes pressés et impatients de communiquer avec succès en français ! Le vocabulaire est simple et usuel et les thèmes, variés, pour faire face, efficacement, à toutes les situations de la vie quotidienne et professionnelle. Livre + CD audio et corrigés inclus. La méthode rapide Vite et bien 1 permet à la fois d'apprendre le français et de découvrir la réalité de la vie en France, les différences culturelles, le langage de la vie quotidienne, le tout en un temps record. En effet, le premier volume couvre, en vingt unités, les niveaux A1 et A2 du Cadre Européen de référence (CECR). Ainsi, en 100 à 120 heures de cours selon les publics, il sera possible d'acquérir une bonne base de grammaire et de vocabulaire, claire, simple, fonctionnelle, et de se sentir à l'aise dans la communication orale et écrite. L'ouvrage s'adresse aux vrais et et aux faux débutants, constituant donc un outil d'apprentissage et/ou de rafraîchissement des connaissances. Chacune des v...

  11. Les biens communs vécus, une finalité non utilitaire

    Directory of Open Access Journals (Sweden)

    François Flahault

    2008-03-01

    Full Text Available Dans cet article, l’auteur présente la notion de « biens communs vécus ». Outre les critères de non-rivalité et de non-exclusion, les biens communs vécus répondent à un troisième critère : le fait d’être plusieurs personnes est la condition pour qu’ils se produisent et pour que chacun en jouisse. De plus, en tant qu’ils sont vécus, ils sont immatériels. L’auteur illustre cette notion par plusieurs exemples, notamment celui de la conversation. Il montre, pour finir, comment cette notion peut contribuer à élargir la pensée écologique au mode d’existence psychique des humains.In this essay, the author discusses the notion of « lived common goods. » Lived common goods must answer three criteria : non-rivalry, non-exclusion, and third, being several persons is the condition for these goods to be produced and experienced. Further, they are immaterial. The author illustrates the notion through a series of examples, one being conversation. Finally, he shows how the notion can contribute to expand ecological thought to human psychic life.

  12. Quantum dot spectroscopy

    DEFF Research Database (Denmark)

    Leosson, Kristjan

    Semiconductor quantum dots ("solid-state atoms") are promising candidates for quantum computers and future electronic and optoelectronic devices. Quantum dots are zero-dimensional electronic systems and therefore have discrete energy levels, similar to atoms or molecules. The size distribution...

  13. Quantum Dots: Theory

    Energy Technology Data Exchange (ETDEWEB)

    Vukmirovic, Nenad; Wang, Lin-Wang

    2009-11-10

    This review covers the description of the methodologies typically used for the calculation of the electronic structure of self-assembled and colloidal quantum dots. These are illustrated by the results of their application to a selected set of physical effects in quantum dots.

  14. Ultrasmall silicon quantum dots

    NARCIS (Netherlands)

    Zwanenburg, F.A.; Van Loon, A.A.; Steele, G.A.; Rijmenam, C.E.W.M.; Balder, T.; Fang, Y.; Lieber, C.M.; Kouwenhoven, L.P.

    2009-01-01

    We report the realization of extremely small single quantum dots in p-type silicon nanowires, defined by Schottky tunnel barriers with Ni and NiSi contacts. Despite their ultrasmall size the NiSi–Si–NiSi nanowire quantum dots readily allow spectroscopy of at least ten consecutive holes, and addition

  15. The global warming, public goods and carbon market; Calentamiento global, bienes publicos y mercado de carbono

    Energy Technology Data Exchange (ETDEWEB)

    Quadri de la Torre, Gabriel [EcoSecurities (Mexico)

    2007-07-15

    The global warming is an issue of the public goods, and demands an outstanding multilateral action, which must to ensure both efficiency and unchanging transition towards an economy of low intensity of carbon. The new system, which is going to replace the Kyoto Protocol, will have compromises for the developing countries and deep implication in the relative competitivity of the nations and companies. [Spanish] El calentamiento global es un problema de bienes publicos que exige una extraordinaria accion multilateral. Esta debe asegurar eficiencia y una transicion fluida hacia una economia de baja intensidad de carbono. El nuevo sistema que sucedera al Protocolo de Kyoto significara compromisos para los paises en vias de desarrollo, y tendra profundas implicaciones en la competitividad relativa de naciones y empresas.

  16. Evolución y factores del consumo de bienes duraderos en tiempos de crisis prolongadas

    Directory of Open Access Journals (Sweden)

    Víctor Omar Dabbagh Rollán

    2015-01-01

    Full Text Available En las llamadas sociedades de consumo, como es el caso de la española, el elemento sustentador de la misma es el propio consumo. Es por ello que se vuelve imprescindible en situaciones de crisis económica como la actual analizar cómo evoluciona el mismo y determinar qué factores intervienen en él con el fin de prever futuros comportamientos e, incluso, tomar medidas para incentivar aquellos que se considere más oportuno. En este estudio, a partir del estudio de la encuesta del Indicador de Confianza del Consumidor del CIS, se pretende analizar estos aspectos en el consumo de bienes duraderos que se realiza en España en los dos últimos años.

  17. Musique du mal, musique du bien dans le théâtre baroque

    OpenAIRE

    Wolf, Robert Erich

    2012-01-01

    Si on cherche le fondement moral commun à la plupart des pièces de théâtre baroques, on le trouvera, il me semble, dans le conflit entre le Bien et le Mal. À l’époque baroque ce conflit prend la forme du débat, du dialogue, de la dialectique ; et, comme il arrive souvent dans l’art, l’opposition entre valeurs morales - ou psychologiques, ce qui au théâtre est équivalent - détermine en grande partie la forme de la pièce : on peut dire même qu’elle forme la pièce. Ce qui distingue l’art théâtra...

  18. Bienestar subjetivo, renta y bienes relacionales. Los determinantes de la felicidad en España

    Directory of Open Access Journals (Sweden)

    Iglesias Vázquez, Emma

    2013-12-01

    Full Text Available In the present paper we analyze the determinants of happiness proxying by subjective welfare. The main objective is twofold: on the one hand, to put to the test the Easterlin’s paradox (the lack of a direct relationship between income and subjective wellbeing at aggregate level and, on the other hand, to weight influence of relational goods in determining happiness. The analytical framework adopts the perspective of happiness economics and the empirical evidence is derived from the estimation of a microeconometric function of happiness applying a Logit model both when using cross sectional and panel data. The results show that in Spanish society income plays a secondary and subjective role, while other variables that are associated directly or indirectly to relational goods are revealed to be very important.En el presente trabajo se analizan los determinantes de la felicidad, entendida esta como satisfacción subjetiva revelada. El principal objetivo tiene un doble componente: por un lado, se trata de contrastar la paradoja de Easterlin para la sociedad española (ausencia de un vínculo directo entre el incremento de la renta per capita y la evolución del bienestar subjetivo revelado a nivel agregado y, por otro, evaluar el papel que desempeñan los bienes relacionales como determinantes de la felicidad. El marco analítico adoptado se encuadra dentro de la denominada happiness economics y la evidencia empírica se deriva de la estimación de una función microeconométrica de la felicidad aplicando un modelo Logit tanto en cortes temporales como en datos de panel. Los resultados obtenidos permiten concluir que en España el ingreso desempeña un papel secundario y subjetivo, mientras que se revelan como importantes las variables asociadas directa o indirectamente a los bienes relacionales.

  19. Problemática sobre la disponibilidad de los Bienes Jurídicos Individuales y Responsabilidades Emergentes

    OpenAIRE

    Ignacio Curbelo Solari

    2013-01-01

    Sobre el concepto de Disponibilidad. Concepto de Bien Jurídico y sus funciones. El Consentimiento. Breve Historia. Bienes Jurídicos Colectivos e Individuales. Naturaleza Jurídica del Consentimiento. Posición de Jescheck, Roxin y Muñoz Conde. Posición de los principales autores nacionales: Prof. Gonzalo Fernández, Miguel Langón, Germán Aller, Pedro Montano. Los requisitos del consentimiento. En la doctrina extranjeraEn la doctrina uruguaya El consentimiento presunto. Requisitos del consentimie...

  20. "Cooperativismo y economía del bien común" (Cooperativism and economy of the common good)

    OpenAIRE

    Alejandro Martínez Charterina

    2013-01-01

    En los últimos años (desde 2010) se está promocionando elmodelo de economía del bien común que muestra un buen número de cooperativascomo ejemplo de lo que promociona en el orden empresarial. Este trabajotrata de destacar el interés de las cooperativas por la mejora social, en general,y en particular en el medio en el que se hacen presentes, trascendiendolos intereses de cada cooperativa singular. Esto queda bien unido a las pretensionesde la Alianza Cooperativa Internacional dirigidas a la p...

  1. Graphene quantum dots

    CERN Document Server

    Güçlü, Alev Devrim; Korkusinski, Marek; Hawrylak, Pawel

    2014-01-01

    This book reflects the current status of theoretical and experimental research of graphene based nanostructures, in particular quantum dots, at a level accessible to young researchers, graduate students, experimentalists and theorists. It presents the current state of research of graphene quantum dots, a single or few monolayer thick islands of graphene. It introduces the reader to the electronic and optical properties of graphite, intercalated graphite and graphene, including Dirac fermions, Berry's phase associated with sublattices and valley degeneracy, covers single particle properties of

  2. Bien faire un cours, un exposé, une conférence

    CERN Document Server

    Brown, George

    1981-01-01

    Le livre de Georges Brown est un livre important pour deux raisons : - Parce qu'il propose à tous les formateurs et enseignants une approche méthodologique de la transmission orale des connaissances. En effet, il ne suffit pas de bien connaître son sujet pour le faire comprendre à son auditoire. Ce livre est conçu pour mener le lecteur pas à pas dans la découverte de son propre style d'explication, de ses points faibles et de ses points forts. - Parce qu'il permet au lecteur, grâce à la pratique des 45 exercices contenus dans l'ouvrage, de faire alterner la réflexion et la performance individuelle avec l'échange d'expériences et l'auto-évaluation des méthodes d'enseignement oral. Ce livre, qui possède toutes les qualités du pragmatisme anglo-saxon, met au service de la formation un outil essentiellement pratique. Il s'adresse donc à tous ceux qui donnent des cours, font des séminaires,ou ont à exposer leurs idées devant un auditoire. EXPLIQUER, C'EST D'ABORD SAVOIR COMMUNIQUER.

  3. Evolución reciente de la industria argentina de bienes de capital

    Directory of Open Access Journals (Sweden)

    RICARDO ORTIZ

    2013-05-01

    Full Text Available Este artículo busca identificar los principales rasgos del desempeño de la industria argentina de bienes de capital desde una perspectiva de mediano plazo. En particular, se hace eje en los aspectos distintivos de la trayectoria sectorial verificada durante la década de los noventa, cuando estuvo en plena vigencia el modelo neoliberal y se atacó al sector de muy diversas maneras y en la fase de la posconvertibilidad iniciada formalmente a comienzos del año 2002 y que dio lugar a un importante ciclo expansivo de la actividad económica con un rol destacado de la industria manufacturera. Abstract This paper aims to identify the main features of the performance of the argentine industry of capital goods from a medium-term perspective. In particular, the focus is placed upon the distinctive aspects of the sectorial trend verified during the nineties, when the neoliberal model was at its highest validity and the sector was attacked in many different ways and at the stage of “posconvertibilidad” formally initiated in early 2002, which led to a significant expansive cycle of the economic activity with an important role of the manufacturing sector.

  4. De las cenizas a la Red: el Periodismo como bien común

    Directory of Open Access Journals (Sweden)

    José Carlos Sendín Gutiérrez

    2014-11-01

    Full Text Available Sampedro nos ofrece y comparte –porque el libro se puede leer en partes también en la red– no sólo y fundamentalmente un alegato a favor del periodismo, sino además, una defensa de un nuevo poder ciudadano y de una nueva democracia. Desde las primeras líneas el lector se siente sacudido por el alto voltaje de los datos, los personajes y el análisis perspicaz de la transformación social que parece apuntarse, pero que hasta ahora nadie había sabido traducir en palabras. Palabras que a veces parecen querer levantar por las solapas al que lee, como diciendo, “entérate, está pasando ahora y es importante que lo descubras”, mientras desarrolla ideas a las que vuelve y recalca, pasados los capítulos, en un ejercicio circular que pretende dejar clara –y lo consigue– la tesis central: ya existe una nueva forma de periodismo entendido como bien común (sí, al igual que el agua o el aire que respiramos, libre, de código abierto y mancomunado. Aire nuevo para una sociedad desencantada, para un periodismo en busca de modelos y para unas aulas donde se forman los futuros profesionales en una universidad maltratada, pero quizá por ello, también sumida en la conformidad de un saber rutinario.

  5. Comunicación política y bien común en tiempo de elecciones

    OpenAIRE

    Pérez-Latre, F.J. (Francisco Javier)

    2015-01-01

    Para que la política funcione es necesaria una comunidad de personas diversas, pero que sienten respeto y admiración mutua y coinciden en el afán de mejorar la sociedad y trabajar por el bien común.

  6. Consumo de bienes culturales: reflexiones sobre un concepto y tres categorías para su análisis

    Directory of Open Access Journals (Sweden)

    Luz María Ortega Villa

    2009-01-01

    Full Text Available En este artículo se revisa la elaboración de lo que aquí se denomina consumo de bienes culturales como concepto alternativo al de consumo cultural. El artículo propone a la vez tres categorías de análisis para el objeto de estudio que el primer concepto define.

  7. TTIP: Análisis jurídico-técnico y su impacto en el comercio de bienes

    OpenAIRE

    Aizpiri Oliván, Martín

    2016-01-01

    El TFG en cuestión trata de abordar desde una perspectiva técnico-jurídica los elementos y procedimientos para liberalizar el comercio que se plantean en el TTIP, con especial mención al comercio de bienes.

  8. Marketing Ético como Fundamento del Bien Común en Organizaciones Humanas

    Directory of Open Access Journals (Sweden)

    Alejandro Fernández Baptista

    2014-01-01

    Full Text Available Los hombres poseen necesidades que deben ser satisfechas con el objeto de lograr una vida cónsona con los principios básicos de dignificación de la persona humana, alimento, vestido, medicamentos, comunicación, entretenimiento, transporte, entre otras, son algunas de las necesidades básicas que los seres humanos día tras día se esfuerzan por cubrir mediante el trabajo digno, utilizando para ello las potencialidades propias de cada quien. Las organizaciones modernas por medio del marketing como proceso administrativo, pretende lograr la satisfacción de tales necesidades por medio de la identificación oportuna de dichos requerimientos, elaborando productos y servicios que los satisfagan al crear una propuesta de valor superior a tales expectativas. Sin embargo, tal propuesta debería estar inmersa dentro de parámetros éticos y morales, las cuales garanticen la correcta utilización de cada uno de los elementos de la mezcla de mercadotecnia, producto, precio, promoción y la distribución. De esta manera los gerentes de marketing al momento de tomar decisiones éticas sobre estos tópicos, permitirían en desarrollo de organizaciones humanas promotoras del bien común dentro del contexto donde se desenvuelvanPalabras Clave: Marketing ético; Bien Común; Organizaciones Humanas. Marketing Ethical as the Foundation of the Common Wealth on Human OrganizationsAbstractThe people have needs that must be met for a life in keeping with the basic principles of dignification of the human person, food, clothing, medicines, communication, entertainment, transportation, among others, are some of the basic needs of human beings every day strive to cover using decent, using work of their own potential each person. Modern organizations marketing as administrative process aims at achieving the satisfaction of those needs in the timely identification of those requirements, developing products and services satisfying them to create a proposal for a value

  9. El derecho a comer: Los alimentos como bien público global

    Directory of Open Access Journals (Sweden)

    Ausín, Txetxu

    2010-10-01

    Full Text Available Eating and drinking are essential needs of every human being in every culture and society, and its lack leads to obvious and objective damage. Therefore, food and water becomes moral in terms of universal human right to eat and drink, one of those rights that give and preserve life. However, humanity lives in a grave and intolerable situation of famine, due to structural factors such as international trade and financial policies, production of biofuels, and the abandonment of consumption agriculture, among others. This scenario requires a deep rethinking of public policy on food and drinking water, departing from its conceptualization as public goods, and not as mere commodities.

    Comer y beber son necesidades esenciales de todo ser humano, en toda cultura y sociedad, y su carencia produce, evidentemente, daños graves y objetivos. Por ello, el alimento y el agua potable devienen en exigencias morales universales en términos del derecho humano a comer y a beber, uno de esos derechos que dan y preservan la vida. Sin embargo, la humanidad vive sumida en una gravísima e intolerable situación de hambruna a la que contribuyen algunos factores estructurales como las políticas comerciales y financieras internacionales, la producción de biocombustibles y el abandono de la agricultura de consumo, entre otros. Este panorama obliga a una profunda reformulación de las políticas públicas sobre el alimento y el agua potable, que partan de su conceptualización como bienes públicos y no meras mercancías.

  10. Quantum dot solar cells

    CERN Document Server

    Wu, Jiang

    2013-01-01

    The third generation of solar cells includes those based on semiconductor quantum dots. This sophisticated technology applies nanotechnology and quantum mechanics theory to enhance the performance of ordinary solar cells. Although a practical application of quantum dot solar cells has yet to be achieved, a large number of theoretical calculations and experimental studies have confirmed the potential for meeting the requirement for ultra-high conversion efficiency. In this book, high-profile scientists have contributed tutorial chapters that outline the methods used in and the results of variou

  11. La Salud en Colombia: ¿Qué tan meritorio y público es este bien o servicio?

    Directory of Open Access Journals (Sweden)

    Carlos Arturo Meza Carvajalino

    2003-11-01

    Full Text Available La controversia en la prestación del servicio de salud en Colombia se plantea desde distintos ámbitos, tanto en las instituciones del Estado como en la esfera académica, situación que afecta el desarrollo de la política del sector de la salud, por encontrarse este servicio asociado y vinculado con los derechos económicos, sociales y culturales. Además por el desconocimiento del principio que en esencia le define como un bien que, por sus características, es meritorio. Lamentablemente, en la práctica se convierte en un bien público preferente.

  12. EL DILEMA DE LA CONTRIBUCIÓN VOLUNTARIA A BIENES PÚBLICOS: UNA REVISIÓN DE TRABAJOS EXPERIMENTALES

    Directory of Open Access Journals (Sweden)

    Luis Alejandro Palacio García

    2014-01-01

    Full Text Available El artículo presenta una revisión de los experimentos realizados sobre bienes públicos apoyados en el mecanismo de contribución voluntaria. La evidencia empírica existente muestra que los individuos no son solo los seres egoístas y competitivos que supone la teoría económica ortodoxa, sino que también son seres bondadosos y altruistas. Aunque los diversos trabajos experimentales concuerdan en la existencia de estos sentimientos catalogados como "bondad", no es claro si los sujetos actúan así para mejorar el bienestar de los demás (altruismo o porque se sienten bien realizando este tipo acciones (satisfacción moral.

  13. Recensión La economía del bien común, de Christian Felber

    Directory of Open Access Journals (Sweden)

    Antonio Fernández Laborda

    2014-03-01

    Full Text Available El autor propone que el sistema económico persiga el mismo fin que el establecido en las normas políticas, es decir, el bien común. Felber parte de la premisa de que las empresas compiten entre ellas y, principalmente, se preocupan por aumentar sus beneficios en su cuenta de resultados. Por ello propone que esos resultados incorporen índices relacionados con valores como el respeto a los derechos humanos, a los derechos de los trabajadores, al medio ambiente y a los valores democráticos como la cooperación entre empresas  que decide practicar esa misma entidad. Toda esta serie de nuevos índices formarían también parte del balance del bien común

  14. "Cooperativismo y economía del bien común" (Cooperativism and economy of the common good

    Directory of Open Access Journals (Sweden)

    Alejandro Martínez Charterina

    2013-01-01

    Full Text Available En los últimos años (desde 2010 se está promocionando elmodelo de economía del bien común que muestra un buen número de cooperativascomo ejemplo de lo que promociona en el orden empresarial. Este trabajotrata de destacar el interés de las cooperativas por la mejora social, en general,y en particular en el medio en el que se hacen presentes, trascendiendolos intereses de cada cooperativa singular. Esto queda bien unido a las pretensionesde la Alianza Cooperativa Internacional dirigidas a la promoción de conductasque puedan llevar a un cambio social y una economía sostenible, quereconocemos como las aspiraciones de conquista del cooperativismo.

  15. Problemática sobre la disponibilidad de los Bienes Jurídicos Individuales y Responsabilidades Emergentes

    Directory of Open Access Journals (Sweden)

    Ignacio Curbelo Solari

    2013-12-01

    Full Text Available Sobre el concepto de Disponibilidad. Concepto de Bien Jurídico y sus funciones. El Consentimiento. Breve Historia. Bienes Jurídicos Colectivos e Individuales. Naturaleza Jurídica del Consentimiento. Posición de Jescheck, Roxin y Muñoz Conde. Posición de los principales autores nacionales: Prof. Gonzalo Fernández, Miguel Langón, Germán Aller, Pedro Montano. Los requisitos del consentimiento. En la doctrina extranjeraEn la doctrina uruguaya El consentimiento presunto. Requisitos del consentimiento presunto.Relevancia del consentimiento en el Derecho Positivo. Derecho extranjero Derecho Uruguayo. Diversas situaciones. El art. 44 del CP. La Vida. El consentimiento y la responsabilidad de los médicos. Las intervenciones transexuales. La Eutanasia La ley 18.473 de Voluntad anticipada. La auto puesta en peligro.

  16. Análisis de los criterios de intervención en Bienes Eclesiásticos

    Directory of Open Access Journals (Sweden)

    María José González López

    2015-06-01

    Full Text Available En este artículo se analizan los criterios con los que se debe abordar la intervención en bienes culturales de procedencia eclesiástica en nuestro país a partir del análisis de los apartados específicos de la normativa dictada por el Estado Español y por la Santa Sede, así como en la concordada mediante acuerdos y convenios suscritos entre ambos.

  17. Carbon nanotube quantum dots

    NARCIS (Netherlands)

    Sapmaz, S.

    2006-01-01

    Low temperature electron transport measurements on individual single wall carbon nanotubes are described in this thesis. Carbon nanotubes are small hollow cylinders made entirely out of carbon atoms. At low temperatures (below ~10 K) finite length nanotubes form quantum dots. Because of its small si

  18. Predictors for dioxin accumulation in residents living in Da Nang and Bien Hoa, Vietnam, many years after Agent Orange use.

    Science.gov (United States)

    Pham, Diem T; Nguyen, Hang M; Boivin, Thomas G; Zajacova, Anna; Huzurbazar, Snehalata V; Bergman, Harold L

    2015-01-01

    Agent Orange (AO) was the main defoliant used by the US in Vietnam from 1961 to 1971; AO was contaminated with dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin, or TCDD). Three major dioxin “hot spots” remain from previous AO storage and use at former US bases at Bien Hoa, Da Nang, and Phu Cat, posing potential health risks for Vietnamese living on or near these hot spots. We evaluated potential risk factors contributing to serum TCDD levels in Vietnamese residents at and near contaminated sites in Da Nang and Bien Hoa, Vietnam. We used multiple linear regression to analyze possible associations of blood dioxin concentrations with demographic, socioeconomic, lifestyle, and dietary risk factors for residents living on or near these hot spots. For the Da Nang study, fish farming on the site, living on property flooded from monsoon rains, and age were among the factors showing significant positive associations with serum TCDD concentrations. For the Bien Hoa study, fish farmers working at this site and their immediate family members had significantly higher serum TCDD concentrations. Our results suggest that water-related activities, especially fish-farming, at the hot spots increased the risk of exposure to dioxin. PMID:25463251

  19. Colloidal Double Quantum Dots.

    Science.gov (United States)

    Teitelboim, Ayelet; Meir, Noga; Kazes, Miri; Oron, Dan

    2016-05-17

    Pairs of coupled quantum dots with controlled coupling between the two potential wells serve as an extremely rich system, exhibiting a plethora of optical phenomena that do not exist in each of the isolated constituent dots. Over the past decade, coupled quantum systems have been under extensive study in the context of epitaxially grown quantum dots (QDs), but only a handful of examples have been reported with colloidal QDs. This is mostly due to the difficulties in controllably growing nanoparticles that encapsulate within them two dots separated by an energetic barrier via colloidal synthesis methods. Recent advances in colloidal synthesis methods have enabled the first clear demonstrations of colloidal double quantum dots and allowed for the first exploratory studies into their optical properties. Nevertheless, colloidal double QDs can offer an extended level of structural manipulation that allows not only for a broader range of materials to be used as compared with epitaxially grown counterparts but also for more complex control over the coupling mechanisms and coupling strength between two spatially separated quantum dots. The photophysics of these nanostructures is governed by the balance between two coupling mechanisms. The first is via dipole-dipole interactions between the two constituent components, leading to energy transfer between them. The second is associated with overlap of excited carrier wave functions, leading to charge transfer and multicarrier interactions between the two components. The magnitude of the coupling between the two subcomponents is determined by the detailed potential landscape within the nanocrystals (NCs). One of the hallmarks of double QDs is the observation of dual-color emission from a single nanoparticle, which allows for detailed spectroscopy of their properties down to the single particle level. Furthermore, rational design of the two coupled subsystems enables one to tune the emission statistics from single photon

  20. Electron correlations in quantum dots

    CERN Document Server

    Tipton, D L J

    2001-01-01

    Quantum dot structures confine electrons in a small region of space. Some properties of semiconductor quantum dots, such as the discrete energy levels and shell filling effects visible in addition spectra, have analogies to those of atoms and indeed dots are sometimes referred to as 'artificial atoms'. However, atoms and dots show some fundamental differences due to electron correlations. For real atoms, the kinetic energy of electrons dominates over their mutual Coulomb repulsion energy and for this reason the independent electron approximation works well. For quantum dots the confining potential may be shallower than that of real atoms leading to lower electron densities and a dominance of mutual Coulomb repulsion over kinetic energy. In this strongly correlated regime the independent electron picture leads to qualitatively incorrect results. This thesis concentrates on few-electron quantum dots in the strongly correlated regime both for quasi-one-dimensional and two-dimensional dots in a square confining p...

  1. Fuzzy Dot Structure of BG-algebras

    OpenAIRE

    Tapan Senapati; Monoranjan Bhowmik; Madhumangal Pal

    2014-01-01

    In this paper, the notions of fuzzy dot subalgebras is introduced together with fuzzy normal dot subalgebras and fuzzy dot ideals of BG-algebras. The homomorphic image and inverse image are investigated in fuzzy dot subalgebras and fuzzy dot ideals of BG-algebras. Also, the notion of fuzzy relations on the family of fuzzy dot subalgebras and fuzzy dot ideals of BG-algebras are introduced with some related properties.

  2. Ética de la convivencia en organizaciones del presente: Base fundamental para alcanzar el bien común

    Directory of Open Access Journals (Sweden)

    Cristina Seijo

    2014-01-01

    Full Text Available El propósito de esta investigación es establecer algunas consideraciones teóricas sobre la ética de la convivencia en las organizaciones de presente, de manera que la gerencia en estas organizaciones se perfile hacia la búsqueda del bien común, en este sentido, el estudio se basa en una metodología cualitativa, de tipo descriptiva y diseño no experimental, mediante un análisis documental, ubicada dentro del área de las Ciencias Sociales.En este sentido, el logro del bien común está asociado a alcanzar una vida en convivencia, esto significa lograr acuerdos mínimos a través del diálogo entre los ciudadanos de manera que se pueda establecer el respeto hacia el otro. La base de tales acuerdos será, necesariamente, la búsqueda del bienestar de la sociedad, es decir, el bien común. Esta idea justifica la necesidad de una ética común, la que conlleva al reconocimiento del otro, aceptar el bienestar del otro, aceptación del otro en nuestro sistema, para lograr la convivencia y alcanzar el bienestar o bien común.Palabras Clave: Ética de la convivencia; bien común; acuerdos mínimos. Ethics of the Living together in organizations of future: fundamental Base to reach the common goodAbstractThis research aims at advancing concepts regarding fellowship ethics in contemporary organizations, in order to organize management around common good practices. The achievement of the common good is thus associated to reaching fellowship, this is to achieve minimal consensus through dialog between citizens and strengthen respect to each other. The base of such consensus will be, necessarily, societal welfare, that is to say, the common good.Keywords: Ethics of the living; common good; minimal agreements.

  3. Quantum Dot Sensitized Photoelectrodes

    OpenAIRE

    Thomas Nann; Thomas J. Macdonald

    2011-01-01

    Quantum Dots (QDs) are promising alternatives to organic dyes as sensitisers for photocatalytic electrodes. This review article provides an overview of the current state of the art in this area. More specifically, different types of QDs with a special focus on heavy-metal free QDs and the methods for preparation and adsorption onto metal oxide electrodes (especially titania and zinc oxide) are discussed. Eventually, the key areas of necessary improvements are identified and assessed.

  4. Quantum Dot Sensitized Photoelectrodes

    Directory of Open Access Journals (Sweden)

    Thomas Nann

    2011-11-01

    Full Text Available Quantum Dots (QDs are promising alternatives to organic dyes as sensitisers for photocatalytic electrodes. This review article provides an overview of the current state of the art in this area. More specifically, different types of QDs with a special focus on heavy-metal free QDs and the methods for preparation and adsorption onto metal oxide electrodes (especially titania and zinc oxide are discussed. Eventually, the key areas of necessary improvements are identified and assessed.

  5. Plasmonic fluorescent quantum dots

    OpenAIRE

    Jin, Yongdong; Gao, Xiaohu

    2009-01-01

    Combining multiple discrete components into a single multifunctional nanoparticle could be useful in a variety of applications. Retaining the unique optical and electrical properties of each component after nanoscale integration is, however, a long-standing problem1,2. It is particularly difficult when trying to combine fluorophores such as semiconductor quantum dots with plasmonic materials such as gold, because gold and other metals can quench the fluorescence3,4. So far, the combination of...

  6. Nanocrystal quantum dots

    CERN Document Server

    Klimov, Victor I

    2010-01-01

    ""Soft"" Chemical Synthesis and Manipulation of Semiconductor Nanocrystals, J.A. Hollingsworth and V.I. Klimov Electronic Structure in Semiconductor Nanocrystals: Optical Experiment, D.J. NorrisFine Structure and Polarization Properties of Band-Edge Excitons in Semiconductor Nanocrystals, A.L. EfrosIntraband Spectroscopy and Dynamics of Colloidal Semiconductor Quantum Dots, P. Guyot-Sionnest, M. Shim, and C. WangMultiexciton Phenomena in Semiconductor Nanocrystals, V.I. KlimovOptical Dynamics in Single Semiconductor Quantum Do

  7. Quantum dot nanostructures

    Directory of Open Access Journals (Sweden)

    Mohamed Henini

    2002-06-01

    These sophisticated technologies for the growth of high quality epitaxial layers of compound semiconductor materials on single crystal semiconductor substrates are becoming increasingly important for the development of the semiconductor electronics industry. This article is intended to convey the flavor of the subject by focusing on the technology and applications of self-assembled quantum dots (QDs and to give an introduction to some of the essential characteristics.

  8. La Protección Jurídica de los Bienes Culturales en el Derecho Español

    Directory of Open Access Journals (Sweden)

    Luis A. Anguita Villanueva

    2004-01-01

    Full Text Available RESUMEN El presente artículo trata de la protección de los bienes que manifiestan elementos o valores de la cultura española. Se define, primero, el concepto y el contenido normativo de los bienes culturales a la luz del derecho positivo, tanto nacional español como supranacional. Se revisan, luego, los antecedentes históricos de la protección de los bienes culturales en el Derecho español, para luego examinar el marco jurídico actual del patrimonio histórico, tanto desde la perspectiva de la normativa supranacional (UNESCO, el Consejo de Europa, la Unión Europea y el Convenio de UNIDROIT, como de la normativa nacional, expresada en la Constitución, el ordenamiento estatal y los ordenamientos autonómicos. El trabajo pone de relieve que la complejidad de la protección de los bienes culturales deriva, en parte, de la dificultad de definir o delimitar el concepto de cultura en la ciencia del Derecho y, por otro lado, de la división político-competencial que se diseña en España a través de la Constitución de 1978, que ha dado pie a una hipertrofia normativa, común a los países de modelo "federal" de distribución de competencias, que dificulta la aplicación por parte de los operadores jurídicos.ABSTRACT The article examines the status of objects which embody elements or values of the Spanish culture. First, the legal notion of cultural objects is defined, considering national and supranational law. We then review the historical background of the protection of cultural objects in Spanish law, turning next to the current legal framework for the protection of the historical patrimony, both from a supranational normative perspective (UNESCO, the Council of Europe, The European Union, and the UNIDROIT agreement, and the Spanish national law found in the Constitution, the national law, and the law of the autonomous regions. Throughout the article the notion is stressed that the complexity we find in the protection of cultural

  9. Las madres del bien morir del Hospital de las Cinco Llagas de Sevilla en el Antiguo Régimen

    OpenAIRE

    Rivasplata Varillas, Paula Ermila

    2014-01-01

    Después del Concilio de Trento, el morir y el purgatorio cobraron gran importancia en la vida de los católicos. En instituciones regidas por la Iglesia como el hospital de las Cinco Llagas de Sevilla surgieron otras personas que ayudaban a los curas a bien morir. Se trataba de la “madre agonizante” que se encargaba de ayudar a las moribundas a morir en paz que ejecutaba desde que el médico o cirujano ordenaba administrar el Santo Óleo de la extremaunción. Esta...

  10. Perspectivas sobre la gobernanza de los bienes y la ciudadanía en la obra de Elinor Ostrom

    OpenAIRE

    Leticia Merino Pérez

    2014-01-01

    Este trabajo reflexiona sobre las principales aportaciones conceptuales y me - todológicas de la obra de Elinor Ostrom, con - siderando el contexto conceptual y político en que emergió y se desarrolló: la polémica con las hegemónicas tesis de Garret Hardin sobre la tragedia de los bienes comunes y la teo - ría de la elección racional. Analiza las ruptu - ras y continuidades de la obra de Ostrom en relación con distintos paradigmas dominantes en las ciencias sociales. Indica también que sus ap...

  11. Recensión La economía del bien común, de Christian Felber

    OpenAIRE

    Antonio Fernández Laborda

    2014-01-01

    El autor propone que el sistema económico persiga el mismo fin que el establecido en las normas políticas, es decir, el bien común. Felber parte de la premisa de que las empresas compiten entre ellas y, principalmente, se preocupan por aumentar sus beneficios en su cuenta de resultados. Por ello propone que esos resultados incorporen índices relacionados con valores como el respeto a los derechos humanos, a los derechos de los trabajadores, al medio ambiente y a los valores democráticos como ...

  12. La gestión de lo común y para el bien común desde las aulas

    OpenAIRE

    Ortiz García, Mercedes; Garay Montañez, Nilda; Gómez Calvo, Verónica; Hidalgo Moratal, Moisés; Carmen PASTOR SEMPERE; Romero-Tarín, Adela

    2014-01-01

    La enseñanza universitaria fruto de la investigación del profesorado, enriquecida con la participación del alumnado, debe servir para realizar una reflexión de cuánto acontece fuera y dentro de las Aulas, para que los alumnos crezcan como expertos profesionales pero también como ciudadanos comprometidos con el servicio al bien común desde el saber y la ética. De ahí que nuestra Red a través de sus distintas disciplinas (Derecho Constitucional, Derecho Administrativo, Ciencia política y de la ...

  13. El emprendimiento social como impulsor del cambio hacia la economía del bien común

    OpenAIRE

    Priede Bergamini, Tiziana; López-Cózar Navarro, Cristina; Platero Jaime, Manuel; Arco Juan, Francisco Javier del; Díaz Ridao, Pedro

    2015-01-01

    En el presente trabajo se realiza un análisis conjunto de la Economía del Bien Común (EBC) y el emprendimiento social, con el objetivo de poner de relieve la relación existente entre ambos. Para ello, se analizan las bases sobre las que se asientan estos conceptos, y se realiza una comparación que permite establecer su conexión, destacando la importancia de elementos clave en el orden económico y en el social, tales como la búsqueda de un crecimiento equilibrado y sostenible, una creciente pr...

  14. Inter-dot coupling effects on transport through correlated parallel coupled quantum dots

    Indian Academy of Sciences (India)

    Shyam Chand; G Rajput; K C Sharma; P K Ahluwalia

    2009-05-01

    Transport through symmetric parallel coupled quantum dot system has been studied, using non-equilibrium Green function formalism. The inter-dot tunnelling with on-dot and inter-dot Coulomb repulsion is included. The transmission coefficient and Landaur–Buttiker like current formula are shown in terms of internal states of quantum dots. The effect of inter-dot tunnelling on transport properties has been explored. Results, in intermediate inter-dot coupling regime show signatures of merger of two dots to form a single composite dot and in strong coupling regime the behaviour of the system resembles the two decoupled dots.

  15. Ingénierie de la maintenance De la conception à l'exploitation d'un bien

    CERN Document Server

    Francastel, Jean-Claude

    2003-01-01

    La maintenance a évolué : d’abord confinée à l’entretien des équipements “réparer“ les pannes puis élargie à leur surveillance “prévoir” les pannes elle est intégrée aujourd’hui dès la phase de conception du produit avec notamment le concept de “maintenabilité” du produit. L’ingénierie de maintenance désigne ce processus d’accompagnement d’un bien industriel durant toutes les phases de son cycle de vie de la conception au démantèlement qui permet d’optimiser l’exploitation de ce bien et son coût global life cycle cost. Cet ouvrage décrit les différentes phases du cycle de vie en exposant les techniques qui permettent d’intégrer à chaque étape les concepts de maintenance.

  16. Tout va bien ! méthode de français : cahier d'exercices 2

    CERN Document Server

    Augé, H; Marlhens, C; Martin, L

    2005-01-01

    Tout va bien ! est une méthode de français destinée aux grands adolescents et adultes débutants ou faux-débutants. Ses objectifs respectent scrupuleusement les recommandations du Cadre européen commun de référence pour les langues, comme en témoigne le portfolio qui accompagne le livre de l'élève. Tout va bien ! propose : Des supports et des situations de communication authentiques ou proches de l'authentique, permettant à l'élève de se sensibiliser aux différents registres et de découvrir certains aspects de la culture francophone tout autant que la langue. De très nombreuses activités visant l'acquisition des quatre compétences de communication et l'utilisation de stratégies spécifiques. Un travail sur la grammaire et le vocabulaire associés aux situations et au service de la communication faisant une large place à l'observation et à la réflexion. Une invitation régulière à l'évaluation, au travail an autonomie et à l'auto-évaluation.

  17. Tout va bien ! méthode de français : cahier d'exercices 1

    CERN Document Server

    Augé, H; Marlhens, C; Martin, L

    2005-01-01

    Tout va bien ! est une méthode de français destinée aux grands adolescents et adultes débutants ou faux-débutants. Ses objectifs respectent scrupuleusement les recommandations du Cadre européen commun de référence pour les langues, comme en témoigne le portfolio qui accompagne le livre de l'élève. Tout va bien ! propose : Des supports et des situations de communication authentiques ou proches de l'authentique, permettant à l'élève de se sensibiliser aux différents registres et de découvrir certains aspects de la culture francophone tout autant que la langue. De très nombreuses activités visant l'acquisition des quatre compétences de communication et l'utilisation de stratégies spécifiques. Un travail sur la grammaire et le vocabulaire associés aux situations et au service de la communication faisant une large place à l'observation et à la réflexion. Une invitation régulière à l'évaluation, au travail an autonomie et à l'auto-évaluation.

  18. Temps de travail et horaires atypiques : Impact sur le conflit travail-famille et le bien-être.

    OpenAIRE

    Hansez, Isabelle; Etienne, Anne-Marie; Breuer, Lara

    2008-01-01

    L’étude présentée propose d’examiner, parmi 184 travailleurs luxembourgeois, le lien entre le temps de travail, y compris les horaires atypiques, l’interaction vie privée-vie professionnelle et le bien-être au travail. Les résultats principaux relèvent un effet significatif (négatif) du travail de week-end, du travail de nuit et des horaires compressés sur l’influence négative travail-famille. Un effet significatif (négatif) de l’horaire compressé sur l’influence positive travail-famille est ...

  19. INDUSTRIA DE BIENES DE EQUIPO DE LA ECONOMÍA ESPAÑOLA: INSERCIÓN COMERCIAL Y CAMBIO ESTRUCTURAL

    Directory of Open Access Journals (Sweden)

    Fernando Luengo

    2011-01-01

    Full Text Available El texto examina el comercio exterior de la industria de bienes de equipo de la economía española en el entorno comunitario. Dicho análisis se realiza a partir de la evolución de un conjunto de indicadores reveladores de la calidad de la inserción comercial, el nivel tecnológico y la posición de gama. La principal conclusión es que, aun aceptando la diversidad de posiciones y trayectorias observadas en la industria, parece que ésta ocupa un espacio relativamente subordinado, instalada en segmentos de mercado de mediabaja tecnología y gama.

  20. La Cultura Corporativa, esencial para el desarrollo de la Economía del Bien Común

    OpenAIRE

    Guerra Carlos, Luis Enrique

    2015-01-01

    La cultura corporativa adquiere actualmente una dimensión relevante como requisito indispensable para el progreso de la Economía del Bien Común: una corriente emergente que propone un nuevo modelo económico basado en la colaboración y una redistribución más equitativa de los recursos para la búsqueda del beneficio social. La integración de esta iniciativa requiere que las compañías sean capaces de adaptar esas ideas a través de su cultura; de su manera de pensar y actuar, y de la alineación e...

  1. Manipulación mediática, identidad juvenil y prostitución de un bien necesario

    OpenAIRE

    Alexander Mosquera

    2007-01-01

    Algo que identifi ca al joven de hoy es la telefonía móvil, una nueva tecnología que invade todas las esferas de lavida pública y privada, cuya presencia se hace sentir a través de una multiplicidad de “ring-tones”. Este trabajo tienecomo objetivo general describir la interrelación que se da entre la manipulación de los medios a través del discursopublicitario sobre celulares, la construcción de la identidad juvenil y la prostitución de lo que otrora fuera un bien necesariocomo el teléfono. S...

  2. Les Nations unies et les biens publics mondiaux : contributions historiques et défis à venir

    Directory of Open Access Journals (Sweden)

    Bruce Jenks

    2012-04-01

    Full Text Available Cet article explore la thèse selon laquelle la contribution la plus importante de l’Organisation des Nations unies (ONU à la production de biens publics mondiaux a été son rôle dans l’instauration d’espaces et de capacités permettant de créer des valeurs communes. Débutant par la Charte elle-même, l’auteur retrace l’évolution de cette contribution à travers différentes phases historiques. Il analyse l’impact de la mondialisation sur le rôle des Nations unies ; il identifie notamment la qualité de la perméabilité en tant que produit de la mondialisation, ce qui est essentiel à la compréhension des défis actuels auxquels font face les Nations unies et également au cœur du programme sur les biens publics mondiaux (BPM. L’article examine brièvement, sous cet angle, l’évolution du rôle des Nations unies dans les domaines de la paix et de la sécurité, des droits de l’homme et de la coopération au développement. En conclusion sont identifiés huit leviers de changement qui détermineront la faculté des Nations unies à contribuer de manière substantielle aux BPM : l’instauration de normes et de valeurs communes, la qualité de la direction, l’amélioration de la gouvernance, un réalignement institutionnel, des financements innovants, le renforcement de la consolidation des instruments juridiques, la concentration sur des points stratégiques et le pouvoir des réseaux.

  3. DISEÑO DE TARIFAS DE BIENES PÚBLICOS LOCALES. CONSIDERACIONES EN TORNO AL CASO DEL AGUA POTABLE

    Directory of Open Access Journals (Sweden)

    Carlos Alberto Gómez Prado

    2013-10-01

    Full Text Available El recurso agua se constituye como un bien de primera necesidad, que no ha sido valorado de manera adecuada. Su valor no contempla los beneficios que genera en términos de bienestar, salud, económicos y ambientales, entre otros. No se explota de manera correcta, desperdiciándolo y contaminándolo indiscriminadamente.En últimas fechas se ha acentuado la discusión sobre la problemática de la disponibilidad del agua, y aunque en algunas regiones se presenta un escenario poco pesimista, es cierto que este recurso no se utiliza adecuadamente; es decir, el problema radica en su gestión y tarifación.El presente trabajo plantea una serie de propuestas metodológicas para asignar un valor tarifario económicamente eficiente al agua potable; se determinará el precio del recurso hídrico mediante la metodología de análisis de los costos reales de producción, intentando asignar un precio que permita solventar los costos medios de producción de largo plazo, así como utilidades que permitan reinversión ante incrementos futuros de la demanda sin afectar el precio.Valga señalar que la asignación de precios al recurso hídrico no se constituye en sí misma como una finalidad; se trata, más bien de la antesala del financiamiento del desarrollo local.

  4. Quantum dots: Rethinking the electronics

    Science.gov (United States)

    Bishnoi, Dimple

    2016-05-01

    In this paper, we demonstrate theoretically that the Quantum dots are quite interesting for the electronics industry. Semiconductor quantum dots (QDs) are nanometer-scale crystals, which have unique photo physical, quantum electrical properties, size-dependent optical properties, There small size means that electrons do not have to travel as far as with larger particles, thus electronic devices can operate faster. Cheaper than modern commercial solar cells while making use of a wider variety of photon energies, including "waste heat" from the sun's energy. Quantum dots can be used in tandem cells, which are multi junction photovoltaic cells or in the intermediate band setup. PbSe (lead selenide) is commonly used in quantum dot solar cells.

  5. Le bien commun : une intention éthique entre la loi du marché et l’individualisme

    OpenAIRE

    Beauchemin, Jacques

    2016-01-01

    Considérer le bien commun du point de vue des objets qu’il recouvre conduit à considérer un ensemble de « biens sociaux » associés à la nature biologique, sociale et politique des individus en société. Or la définition du bien commun ne réside pas seulement dans les objets auxquels on peut l’associer mais surtout dans la capacité collective à faire de la société un projet éthique de vivre ensemble. Ainsi, l’atomisation de la société que provoquent la marchandisation et l’individualisme contre...

  6. La protección de bienes urbanos. Avances en la política pública de Medellín

    Directory of Open Access Journals (Sweden)

    Clara In��s Atehortúa-Arredondo

    2010-12-01

    Full Text Available La problemática de la protección de bienes en el país es una pregunta obligatoria para quienes tienen dentro de su labor el reconocimiento, la restitución y la reparación de las víctimas del desplazamiento forzado. Uno de los puntos que deben analizarse dentro de esta problemática es lo concerniente a la protección de bienes urbanos y cuya responsabilidad está en cabeza de los municipios. El desarrollo de una política pública por parte de la ciudad de Medellín para la protección de bienes es un avance significativo para la construcción de protocolos y para la reivindicación de derechos de quienes han abandonado por causa de la violencia o han sido despojados de sus viviendas en lo urbano.

  7. Photonics of shungite quantum dots

    OpenAIRE

    Razbirin, Boris S.; Rozhkova, Natalia N.; Sheka, Elena F.

    2014-01-01

    Shungite quantum dots are associated with nanosize fragments of reduced graphene oxide similarly to synthetic graphene quantum dots thus forming a common class of GQDs. Colloidal dispersions of powdered shungite in water, carbon tetrachloride, and toluene form the ground for the GQD photonic peculiarities manifestation. Morphological study shows a steady trend of GQDs to form fractals and a drastic change in the colloids fractal structure caused by solvent was reliably established. Spectral s...

  8. Spin pumping through quantum dots

    OpenAIRE

    Rojek, Stephan; Governale, Michele; König, Jürgen

    2013-01-01

    We propose schemes for generating spin currents into a semiconductor by adiabatic or non-adiabatic pumping of electrons through interacting quantum dots. The appeal of such schemes lies in the possibility to tune the pumping characteristics via gate voltages that control the properties of the quantum dot. The calculations are based on a systematic perturbation expansion in the tunnel-coupling strength and the pumping frequency, expressed within a diagrammatic real-time technique. Special focu...

  9. Quadra-Quantum Dots and Related Patterns of Quantum Dot Molecules: Basic Nanostructures for Quantum Dot Cellular Automata Application

    Directory of Open Access Journals (Sweden)

    Somsak Panyakeow

    2010-10-01

    Full Text Available Laterally close-packed quantum dots (QDs called quantum dot molecules (QDMs are grown by modified molecular beam epitaxy (MBE. Quantum dots could be aligned and cross hatched. Quantum rings (QRs created from quantum dot transformation during thin or partial capping are used as templates for the formations of bi-quantum dot molecules (Bi-QDMs and quantum dot rings (QDRs. Preferable quantum dot nanostructure for quantum computation based on quantum dot cellular automata (QCA is laterally close-packed quantum dot molecules having four quantum dots at the corners of square configuration. These four quantum dot sets are called quadra-quantum dots (QQDs. Aligned quadra-quantum dots with two electron confinements work like a wire for digital information transmission by Coulomb repulsion force, which is fast and consumes little power. Combination of quadra-quantum dots in line and their cross-over works as logic gates and memory bits. Molecular Beam Epitaxial growth technique called 'Droplet Epitaxy' has been developed for several quantum nanostructures such as quantum rings and quantum dot rings. Quantum rings are prepared by using 20 ML In-Ga (15:85 droplets deposited on a GaAs substrate at 390'C with a droplet growth rate of 1ML/s. Arsenic flux (7'8'10-6Torr is then exposed for InGaAs crystallization at 200'C for 5 min. During droplet epitaxy at a high droplet thickness and high temperature, out-diffusion from the centre of droplets occurs under anisotropic strain. This leads to quantum ring structures having non-uniform ring stripes and deep square-shaped nanoholes. Using these peculiar quantum rings as templates, four quantum dots situated at the corners of a square shape are regrown. Two of these four quantum dots are aligned either or, which are preferable crystallographic directions of quantum dot alignment in general.

  10. Determinación de los precios implícitos en bienes inmuebles : una alternativa a la modelización hedónica

    OpenAIRE

    Ceular Villamandos, Nuria; Caridad y Ocerin, José María

    2004-01-01

    RESUMEN Recientemente un nuevo enfoque para estimar el valor de bienes inmuebles está siendo cada vez más usado. Para ello se usan atributos internos del bien, y externos, del entorno, pues ambos son percibidos de forma diferente en el mercado. Así pues, propiedades con nivel de precios similar son consideradas como claramente diferenciadas en los mercados inmobiliarios. Las técnicas de Inteligencia Arti cial proporcionan nuevas posibilidades, en comparación con la modelización econométrica ...

  11. Los bienes habices y la repoblación de Andalucía en el siglo XIII : el caso de Sevilla

    OpenAIRE

    García Sanjuán, Alejandro

    1999-01-01

    Los legados piadosos o bienes habices constituyen una de las instituciones socioeconómicas islámicas más relevantes durante la Edad Media. Dichos bienes, jurídicamente inalienables, proceden de donaciones voluntarias realizadas por los creyentes musulmanes para cualquier finalidad considerada piadosa desde un punto de vista islámico, de manera particular a favor de pobres y enfermos, para el rescate de prisioneros, para contribuir al sostenimiento de las fronteras y al esfuerzo por defender ...

  12. Administración económica del distrito inquisitorial de Valencia: la receptoría de bienes confiscados (1482-1493)

    OpenAIRE

    Tomás Botella, Bernardo

    2016-01-01

    El objeto de esta tesis doctoral es la receptoría de bienes confiscados de la Inquisición de Valencia, su estructura burocrática y sus procedimientos de actuación sobre la sociedad valenciana bajomedieval. Esta oficina se encargaba de ejecutar el secuestro y confiscación del patrimonio de los herejes condenados, así como de gestionar y liquidar dichos bienes una vez incorporados al fisco regio. Además, se ha analizado la evolución institucional que experimentó el Santo Oficio durante el perio...

  13. Fuzzy dot ideals and fuzzy dot H-ideals of BCH-algebras

    Institute of Scientific and Technical Information of China (English)

    PENG Jia-yin

    2008-01-01

    The notions of fuzzy dot ideals and fuzzy dot H-ideals in BCH-algebras are intro duced,several appropriate examples are provided,and their some properties are investigated.The relations among fuzzy ideal,fuzzy H-ideal,fuzzy dot ideal and fuzzy dot H-ideals in BCH algebras are discussed,several equivalent depictions of fuzzy dot ideal are obtained. How to deal with the homomorphic image and inverse image of fuzzy dot ideals (fuzzy dot H-ideals) are studied. The relations between a fuzzy dot ideal (fuzzy dot H-ideal) in BCH-algebras and a fuzzy dot ideal (fuzzy dot H-ideal) in the product algebra of BCH-algebras are given.

  14. Single to quadruple quantum dots with tunable tunnel couplings

    Energy Technology Data Exchange (ETDEWEB)

    Takakura, T.; Noiri, A.; Obata, T.; Yoneda, J.; Yoshida, K. [Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Otsuka, T.; Tarucha, S. [Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); RIKEN, Center for Emergent Matter Science, 3-1 Wako-shi, Saitama 351-0198 (Japan)

    2014-03-17

    We prepare a gate-defined quadruple quantum dot to study the gate-tunability of single to quadruple quantum dots with finite inter-dot tunnel couplings. The measured charging energies of various double dots suggest that the dot size is governed by the gate geometry. For the triple and quadruple dots, we study the gate-tunable inter-dot tunnel couplings. For the triple dot, we find that the effective tunnel coupling between side dots significantly depends on the alignment of the center dot potential. These results imply that the present quadruple dot has a gate performance relevant for implementing spin-based four-qubits with controllable exchange couplings.

  15. El castellano bien templado

    OpenAIRE

    Sáenz, Miguel

    2009-01-01

    Este artículo se sirve de la música para establecer un paralelismo entre ésta y la traducción, pues si la traducción es una interpretación (musical) de un texto, puede haber innumerables traducciones válidas, pudiendo haber alguna “de referencia”. Además, se plantea que las facultades son como conservatorios donde los futuros traductores estudian técnicas y aprenden fundamentos teóricos (que compara con el solfeo, la armonía y la composición) y que las traducciones “envejecen” porque su es...

  16. El consumo de bienes religiosos. Una introducción económica al caso español

    Directory of Open Access Journals (Sweden)

    Brañas-Garza, Pablo

    2003-08-01

    Full Text Available This paper uses the Economic of Religion issues to explore Spanish religious behaviour. Under this microeconomic framework religious practise is considered "rational" using Azzi-Ehrenberg (1975 arguments: salvation, social and professional motives. We test if that hypotheses may explain Spanish religious activity. To this end we run descriptive and multivariate analysis that allows us to conclude the following: theoretical models well perform Spanish data; gender, ageing, family size and education are positive determinant of church-attendance; the influence of parents behaviour on children religious activity.

    Este trabajo explora el comportamiento religioso de los españoles desde el enfoque de la Economía de la Religión. En un marco microeconómico y utilizando los argumentos de Azzi- Ehrenberg (1975 —motivo salvación, consumo y profesional—, la práctica religiosa resulta racional. En esta investigación estudiamos si estas hipótesis pueden explicar el comportamiento religioso de los españoles. Para ello se realizan análisis descriptivos y multivariantes que nos permiten concluir que: los modelos teóricos explican bien los datos españoles; que el sexo, la edad, el tamaño de la familia y la educación son determinantes positivos de la asistencia a iglesia; que el ejemplo de los padres influye en la actividad religiosa actual de los hijos.

  17. La sucesión a los bienes de Juan Antonio Llorente, en París

    Directory of Open Access Journals (Sweden)

    de la Lama, Enrique

    2003-06-01

    Full Text Available Llorente, one of the most famous critics of the Spanish Inquisition, «afrancesado » in top responsibility and well known in his own physical feature wich Goya made of him, died without leaving his last will. The present work studies in detail the notary documents referring to «succesio ab intestato», wich permit to know his library, his personal belongings as well as information about an illegitimate daughter born in France during his exile.

    Llorente, uno de los más afamados críticos de la Inquisición de España, afrancesado de alta responsabilidad y bien conocido en su mismo semblante físico por el retrato que le hizo Goya, falleció sin hacer testamento. El presente trabajo estudia detalladamente los documentos notariales de la sucesión «ab intestato», que permiten conocer su biblioteca y sus enseres personales, así como la noticia de una hija natural nacida en Francia durante su exilio.

  18. Créations graphiques réussissez vos brochures, logos, pages web, newsletters, flyers, et bien plus encore !

    CERN Document Server

    McWade, John

    2010-01-01

    Dans cet ouvrage, qui regroupe un florilège des meilleurs projets professionnels publiés dans son célèbre magazine de graphisme, Before & After, John McWade offre une présentation approfondie des principes de base du graphisme, avant de partager concrètement techniques et procédés. Dans un style simple et convivial, il analyse différentes créations graphiques abouties – brochures, lettres d'information, sites web, cartes de visite et autres supports visuels – et explique le pourquoi et le comment de leur réussite. À votre tour, inspirez-vous de ces exemples et employez ces mêmes techniques à l'envie pour améliorer vos propres documents. Vous apprendrez à: rogner des photos pour parfaire leur fonction et leur signification; attirer le regard du lecteur à l'emplacement souhaité à l'aide de huit solutions différentes; travailler sur les composants de base de la création graphique, tels que le trait, la forme, la direction, le mouvement, la mise à l'échelle, la couleur, et bien d'a...

  19. Optical Fiber Sensing Using Quantum Dots

    OpenAIRE

    Faramarz Farahi; José Luís Santos; Tito Trindade; Manuel António Martins; Pedro Jorge

    2007-01-01

    Recent advances in the application of semiconductor nanocrystals, or quantum dots, as biochemical sensors are reviewed. Quantum dots have unique optical properties that make them promising alternatives to traditional dyes in many luminescence based bioanalytical techniques. An overview of the more relevant progresses in the application of quantum dots as biochemical probes is addressed. Special focus will be given to configurations where the sensing dots are incorporated in sol...

  20. A colloidal quantum dot spectrometer

    Science.gov (United States)

    Bao, Jie; Bawendi, Moungi G.

    2015-07-01

    Spectroscopy is carried out in almost every field of science, whenever light interacts with matter. Although sophisticated instruments with impressive performance characteristics are available, much effort continues to be invested in the development of miniaturized, cheap and easy-to-use systems. Current microspectrometer designs mostly use interference filters and interferometric optics that limit their photon efficiency, resolution and spectral range. Here we show that many of these limitations can be overcome by replacing interferometric optics with a two-dimensional absorptive filter array composed of colloidal quantum dots. Instead of measuring different bands of a spectrum individually after introducing temporal or spatial separations with gratings or interference-based narrowband filters, a colloidal quantum dot spectrometer measures a light spectrum based on the wavelength multiplexing principle: multiple spectral bands are encoded and detected simultaneously with one filter and one detector, respectively, with the array format allowing the process to be efficiently repeated many times using different filters with different encoding so that sufficient information is obtained to enable computational reconstruction of the target spectrum. We illustrate the performance of such a quantum dot microspectrometer, made from 195 different types of quantum dots with absorption features that cover a spectral range of 300 nanometres, by measuring shifts in spectral peak positions as small as one nanometre. Given this performance, demonstrable avenues for further improvement, the ease with which quantum dots can be processed and integrated, and their numerous finely tuneable bandgaps that cover a broad spectral range, we expect that quantum dot microspectrometers will be useful in applications where minimizing size, weight, cost and complexity of the spectrometer are critical.

  1. Quantum-dot emitters in photonic nanostructures

    DEFF Research Database (Denmark)

    Hvam, Jørn Märcher; Stobbe, Søren; Lodahl, Peter

    2010-01-01

    The spontaneous emission from self-assembled semiconductor quantum dots is strongly influenced by the environment in which they are placed. This can be used to determine fundamental optical properties of the quantum dots as well as to manipulate and control the quantum-dot emission itself....

  2. Beer's law in semiconductor quantum dots

    CERN Document Server

    Adamashvili, G T

    2010-01-01

    The propagation of a coherent optical linear wave in an ensemble of semiconductor quantum dots is considered. It is shown that a distribution of transition dipole moments of the quantum dots changes significantly the polarization and Beer's absorption length of the ensemble of quantum dots. Explicit analytical expressions for these quantities are presented.

  3. Manipulación mediática, identidad juvenil y prostitución de un bien necesario

    Directory of Open Access Journals (Sweden)

    Alexander Mosquera

    2007-01-01

    Full Text Available Algo que identifi ca al joven de hoy es la telefonía móvil, una nueva tecnología que invade todas las esferas de lavida pública y privada, cuya presencia se hace sentir a través de una multiplicidad de “ring-tones”. Este trabajo tienecomo objetivo general describir la interrelación que se da entre la manipulación de los medios a través del discursopublicitario sobre celulares, la construcción de la identidad juvenil y la prostitución de lo que otrora fuera un bien necesariocomo el teléfono. Se abordó un corpus compuesto por varios avisos publicitarios que circularon en los diariosvenezolanos El Nacional, La Verdad y Panorama durante agosto de 2005, desde la perspectiva teórico-metodológicade la semiótica crítica de González de Ávila y de la semiótica de la cultura de Lotman. También se utilizaron algunosaportes de Magariños de Morentin relacionados con la semiótica de los mensajes publicitarios, así como los de Caro Almela, Bourdieu, Pasquali y Eco sobre los mass-media. Los resultados revelaron una manipulación mediática a través del discurso publicitario, dirigida a crear la urgente necesidad de poseer un celular, porque éste es el signo-mercancía con el cual se identifi ca el joven actual. Una conclusión preliminar indica que la no-posesión de ese aparato hace aparecer al joven como un “excluido” de ese mundo de la telefonía móvil.

  4. Spin storage in quantum dot ensembles and single quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Heiss, Dominik

    2009-10-15

    This thesis deals with the investigation of spin relaxation of electrons and holes in small ensembles of self-assembled quantum dots using optical techniques. Furthermore, a method to detect the spin orientation in a single quantum dot was developed in the framework of this thesis. A spin storage device was used to optically generate oriented electron spins in small frequency selected quantum dot ensembles using circularly polarized optical excitation. The spin orientation can be determined by the polarization of the time delayed electroluminescence signal generated by the device after a continuously variable storage time. The degree of spin polarized initialization was found to be limited to 0.6 at high magnetic fields, where anisotropic effects are compensated. The spin relaxation was directly measured as a function of magnetic field, lattice temperature and s-shell transition energy of the quantum dot by varying the spin storage time up to 30 ms. Very long spin lifetimes are obtained with a lower limit of T{sub 1}=20 ms at B=4 T and T=1 K. A strong magnetic field dependence T{sub 1}{proportional_to}B{sup -5} has been observed for low temperatures of T=1 K which weakens as the temperature is increased. In addition, the temperature dependence has been determined with T{sub 1}{proportional_to}T{sup -1}. The characteristic dependencies on magnetic field and temperature lead to the identification of the spin relaxation mechanism, which is governed by spin-orbit coupling and mediated by single phonon scattering. This finding is qualitatively supported by the energy dependent measurements. The investigations were extended to a modified device design that enabled studying the spin relaxation dynamics of heavy holes in self-assembled quantum dots. The measurements show a polarization memory effect for holes with up to 0.1 degree of polarization. Furthermore, investigations of the time dynamics of the hole spin relaxation reveal surprisingly long lifetimes T{sub 1}{sup h

  5. Spin storage in quantum dot ensembles and single quantum dots

    International Nuclear Information System (INIS)

    This thesis deals with the investigation of spin relaxation of electrons and holes in small ensembles of self-assembled quantum dots using optical techniques. Furthermore, a method to detect the spin orientation in a single quantum dot was developed in the framework of this thesis. A spin storage device was used to optically generate oriented electron spins in small frequency selected quantum dot ensembles using circularly polarized optical excitation. The spin orientation can be determined by the polarization of the time delayed electroluminescence signal generated by the device after a continuously variable storage time. The degree of spin polarized initialization was found to be limited to 0.6 at high magnetic fields, where anisotropic effects are compensated. The spin relaxation was directly measured as a function of magnetic field, lattice temperature and s-shell transition energy of the quantum dot by varying the spin storage time up to 30 ms. Very long spin lifetimes are obtained with a lower limit of T1=20 ms at B=4 T and T=1 K. A strong magnetic field dependence T1∝B-5 has been observed for low temperatures of T=1 K which weakens as the temperature is increased. In addition, the temperature dependence has been determined with T1∝T-1. The characteristic dependencies on magnetic field and temperature lead to the identification of the spin relaxation mechanism, which is governed by spin-orbit coupling and mediated by single phonon scattering. This finding is qualitatively supported by the energy dependent measurements. The investigations were extended to a modified device design that enabled studying the spin relaxation dynamics of heavy holes in self-assembled quantum dots. The measurements show a polarization memory effect for holes with up to 0.1 degree of polarization. Furthermore, investigations of the time dynamics of the hole spin relaxation reveal surprisingly long lifetimes T1h in the microsecond range, therefore, comparable with electron spin

  6. Luminescent Surface Quaternized Carbon Dots

    KAUST Repository

    Bourlinos, Athanasios B.

    2012-01-10

    Thermal oxidation of a salt precursor made from the acid base combination of tris(hydroxymethyl)aminomethane and betaine hydrochloride results in light-emitting surface quaternized carbon dots that are water-dispersible, display anion exchange properties, and exhibit uniform size/surface charge. © 2011 American Chemical Society.

  7. On triaxial ellipsoidal quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Voon, L C Lew Yan; Willatzen, M [Mads Clausen Institute, University of Southern Denmark, Grundtvigs Alle 150, DK-6400 Soenderborg (Denmark)

    2004-02-25

    The bound-state problem for triaxial ellipsoidal infinite-barrier quantum dots has been solved. It is exactly solvable in terms of ellipsoidal coordinates and the eigenmodes are written in terms of Lame wavefunctions. The need for all eight types of functions is shown. This presents a generalization over previous work on spheres and spheroids. Splitting of degeneracy and level crossing are obtained.

  8. DOT strategies versus orbiter strategies

    NARCIS (Netherlands)

    Rutten, R.J.

    2001-01-01

    The Dutch Open Telescope is a high-resolution solar imager coming on-line at La Palma. The definition of the DOT science niche, strategies, and requirements resemble Solar Orbiter considerations and deliberations. I discuss the latter in the light of the former, and claim that multi-line observation

  9. Vertical asymmetric double quantum dots

    Science.gov (United States)

    Roßbach, R.; Reischle, M.; Beirne, G. J.; Schweizer, H.; Jetter, M.; Michler, P.

    2007-01-01

    Two layers of differently sized self-assembled InP-quantum dots (QDs) separated by a GaInP spacer layer with varying thickness were grown by metal organic vapor phase epitaxy (MOVPE). Photoluminescence measurements of the QD ensembles and of individual asymmetric double QDS show coupling due to the tunnelling of carriers.

  10. Hyperdense dots mimicking microcalcifications : Mammographic findings

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Nam Hyeon; Park, Jeong Mi; Goo, Hyun Woo; Bang, Sun Woo [Asan Medical Center, University of Ulsan College of Medicine, Seoul (Korea, Republic of)

    1996-12-01

    To differentiate fine hyperdense dots mimicking microcalcifications from true microcalcifications on mammography. Mammograms showing hyperdense dots in ten patients (mean age, 59 years) were evaluated. Two radiologists were asked to differentiate with the naked eye the hyperdense dots seen on ten mammograms and proven microcalcifications seen on ten mammograms. Densitometry was also performed for all lesions and the contrast index was calculated. The shape and distribution of the hyperdense dots were evaluated and enquires were made regarding any history of breast disease and corresponding treatment. Biopsies were performed for two patients with hyperdense dots. Two radiologists made correct diagnoses in 19/20 cases(95%). The contrast index was 0.10-0.88 (mean 0.58) for hyperdense dots and 0.02-0.45 (mean 0.17) for true microcalcifications. The hyperdense dots were finer and homogeneously rounder than the microcalcifications. Distribution of the hyperdense dots was more superficial in subcutaneous fat (seven cases) and subareolar area (six cases). All ten patients with hyperdense dots had history of mastitis and abscesses and had been treated by open drainage (six cases) and/or folk remedy (four cases). In eight patients, herb patches had been attached. Biopsies of hyperdense dots did not show any microcalcification or evidence of malignancy. These hyperdense dots were seen mainly in older patients. Their characteristic density, shape, distribution and clinical history makes differential diagnosis from true microcalcifications easy and could reduce unnecessary diagnostic procedures such as surgical biopsy.

  11. Hyperdense dots mimicking microcalcifications : Mammographic findings

    International Nuclear Information System (INIS)

    To differentiate fine hyperdense dots mimicking microcalcifications from true microcalcifications on mammography. Mammograms showing hyperdense dots in ten patients (mean age, 59 years) were evaluated. Two radiologists were asked to differentiate with the naked eye the hyperdense dots seen on ten mammograms and proven microcalcifications seen on ten mammograms. Densitometry was also performed for all lesions and the contrast index was calculated. The shape and distribution of the hyperdense dots were evaluated and enquires were made regarding any history of breast disease and corresponding treatment. Biopsies were performed for two patients with hyperdense dots. Two radiologists made correct diagnoses in 19/20 cases(95%). The contrast index was 0.10-0.88 (mean 0.58) for hyperdense dots and 0.02-0.45 (mean 0.17) for true microcalcifications. The hyperdense dots were finer and homogeneously rounder than the microcalcifications. Distribution of the hyperdense dots was more superficial in subcutaneous fat (seven cases) and subareolar area (six cases). All ten patients with hyperdense dots had history of mastitis and abscesses and had been treated by open drainage (six cases) and/or folk remedy (four cases). In eight patients, herb patches had been attached. Biopsies of hyperdense dots did not show any microcalcification or evidence of malignancy. These hyperdense dots were seen mainly in older patients. Their characteristic density, shape, distribution and clinical history makes differential diagnosis from true microcalcifications easy and could reduce unnecessary diagnostic procedures such as surgical biopsy

  12. Systematic safety evaluation on photoluminescent carbon dots

    Science.gov (United States)

    Wang, Kan; Gao, Zhongcai; Gao, Guo; Wo, Yan; Wang, Yuxia; Shen, Guangxia; Cui, Daxiang

    2013-03-01

    Photoluminescent carbon dots (C-dots) were prepared using the improved nitric acid oxidation method. The C-dots were characterized by tapping-mode atomic force microscopy, and UV-vis absorption spectroscopy. The C-dots were subjected to systematic safety evaluation via acute toxicity, subacute toxicity, and genotoxicity experiments (including mouse bone marrow micronuclear test and Salmonella typhimurium mutagenicity test). The results showed that the C-dots were successfully prepared with good stability, high dispersibility, and water solubility. At all studied C-dot dosages, no significant toxic effect, i.e., no abnormality or lesion, was observed in the organs of the animals. Therefore, the C-dots are non-toxic to mice under any dose and have potential use in fluorescence imaging in vivo, tumor cell tracking, and others.

  13. Spin transport through quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Lima, A.T. da Cunha; Anda, Enrique V. [Pontificia Univ. Catolica do Rio de Janeiro (PUC-Rio), RJ (Brazil)

    2003-07-01

    Full text: We investigate the spin polarized transport properties of a nanoscopic device constituted by a quantum dot connected to two leads. The electrical current circulates with a spin polarization that is modulated via a gate potential that controls the intensity of the spin-orbit coupling, the Rashba effect. We study a polarized field-effect transistor when one of its parts is constituted by a small quantum dot, which energies are controlled by another gate potential operating inside the confined region. The high confinement and correlation suffered by the charges inside the dot gives rise to novel phenomena. We show that through the manipulation of the gate potential applied to the dot it is possible to control, in a very efficient way, the intensity and polarization of the current that goes along the system. Other crucial parameters to be varied in order to understand the behavior of this system are the intensity of the external applied electric and magnetic field. The system is represented by the Anderson Impurity Hamiltonian summed to a spin-orbit interaction, which describes the Rashba effect. To obtain the current of this out-of-equilibrium system we use the Keldysh formalism.The solution of the Green function are compatible with the Coulomb blockade regime. We show that under the effect of a external magnetic field, if the dot is small enough the device operates as a complete spin filter that can be controlled by the gate potential. The behavior of this device when it is injected into it a polarized current and modulated by the Rashba effect is as well studied. (author)

  14. “Jeneros de gusto y sobretodos ingleses”: el impacto cultural del consumo de bienes ingleses por la clase alta bogotana .

    Directory of Open Access Journals (Sweden)

    Ana Maria Otero Cleves.

    2009-05-01

    Full Text Available Este artículo analiza el impacto cultural del consumo de bienes Inglés por la clase alta de Bogotá durante el siglo XIX. Se sugiere que el consumo de productos Inglés después de la independencia del país fue uno de los principales mecanismos empleados por las clases altas para asegurar su posición social, así como para construir una nación moderna, de acuerdo a las normas europeas. Por lo tanto, el artículo analiza el papel que el consumo de bienes extranjeros en el proceso de construcción de la nación y la diferenciación social en el siglo XIX.

  15. Palpitando la modernidad: el negocio de bienes raíces en Cali (Colombia a partir del caso de Jorge Garcés Borrero, 1900-1944

    Directory of Open Access Journals (Sweden)

    María Fernanda Erazo Obando

    2014-01-01

    Full Text Available El objetivo del presente artículo es analizar el movimiento de compra y venta de bienes raíces en Cali (Colombia durante la primera mitad del siglo XX. Para ello, se toma como referencia la empresa del comerciante Jorge Garcés Borrero, la cual, se enfocó principalmente en la ejecución de este tipo de negocios. Dicha empresa, a pesar de no haberse constituido legal y jurídicamente, presentó las características de una compañía como tal, generando importantes inversiones y ganancias a partir del mercado de bienes. Apoyados en fuentes notariales se explica el desarrollo de esta actividad comercial entre 1900-1944.

  16. Palpitando la modernidad: el negocio de bienes raíces en Cali (Colombia a partir del caso de Jorge Garcés Borrero, 1900-1944

    Directory of Open Access Journals (Sweden)

    María Fernanda Erazo Obando

    2014-07-01

    Full Text Available El objetivo del presente artículo es analizar el movimiento de compra y venta de bienes raíces en Cali (Colombia durante la primera mitad del siglo XX. Para ello, se toma como referencia la empresa del comerciante Jorge Garcés Borrero, la cual, se enfocó principalmente en la ejecución de este tipo de negocios. Dicha empresa, a pesar de no haberse constituido legal y jurídicamente, presentó las características de una compañía como tal, generando importantes inversiones y ganancias a partir del mercado de bienes. Apoyados en fuentes notariales se explica el desarrollo de esta actividad comercial entre 1900-1944.

  17. Negros y pardos propietarios de bienes raíces y de esclavos en el Buenos Aires de fines del período hispánico

    Directory of Open Access Journals (Sweden)

    Rosal, Miguel A.

    2001-12-01

    Full Text Available El trabajo pretende ilustrar un aspecto poco conocido dentro de la problemática afroporteña; nos referimos a la capacidad para adquirir bienes inmuebles —terrenos y casas— y esclavos que tenían los integrantes de la raza africana, en general de condición libre, pero también esclavizados, en el Buenos Aires tardocolonial, capacidad fundada sin duda en una significativa actividad laboral y, en especial, artesanal. En ese sentido, hacemos referencia a las características de los inmuebles, a los precios de los mismos, a su ubicación en el espacio urbano (distribución de los afroporteños según los barrios y, por último, a la participación de negros y blancos en el mercado porteño de compraventa de bienes raíces y de esclavos.

  18. Quadra-quantum Dots and Related Patterns of Quantum Dot Molecules:

    Directory of Open Access Journals (Sweden)

    Somsak Panyakeow

    2010-10-01

    Full Text Available Abstract Laterally close-packed quantum dots (QDs called quantum dot molecules (QDMs are grown by modified molecular beam epitaxy (MBE. Quantum dots could be aligned and cross hatched. Quantum rings (QRs created from quantum dot transformation during thin or partial capping are used as templates for the formations of bi-quantum dot molecules (Bi-QDMs and quantum dot rings (QDRs. Preferable quantum dot nanostructure for quantum computation based on quantum dot cellular automata (QCA is laterally close-packed quantum dot molecules having four quantum dots at the corners of square configuration. These four quantum dot sets are called quadra-quantum dots (QQDs. Aligned quadra-quantum dots with two electron confinements work like a wire for digital information transmission by Coulomb repulsion force, which is fast and consumes little power. Combination of quadra-quantum dots in line and their cross-over works as logic gates and memory bits. Molecular Beam Epitaxial growth technique called ‘‘Droplet Epitaxy” has been developed for several quantum nanostructures such as quantum rings and quantum dot rings. Quantum rings are prepared by using 20 ML In-Ga (15:85 droplets deposited on a GaAs substrate at 390°C with a droplet growth rate of 1ML/s. Arsenic flux (7–8×10-6Torr is then exposed for InGaAs crystallization at 200°C for 5 min. During droplet epitaxy at a high droplet thickness and high temperature, out-diffusion from the centre of droplets occurs under anisotropic strain. This leads to quantum ring structures having non-uniform ring stripes and deep square-shaped nanoholes. Using these peculiar quantum rings as templates, four quantum dots situated at the corners of a square shape are regrown. Two of these four quantum dots are aligned either or , which are preferable crystallographic directions of quantum dot alignment in general.

  19. La economía social y solidaria como alternativa económica. Bienes comunes y democracia

    Directory of Open Access Journals (Sweden)

    Jaime Abad Montesinos

    2014-10-01

    Full Text Available Normal 0 21 MicrosoftInternetExplorer4 Resumen: El presente artículo trata de enmarcar la economía social y solidaria en el seno del actual debate producto de la crisis económica vigente, haciendo especial hincapié en las cuestiones relacionadas con los bienes comunes y la gestión democrática. La crisis presente ha puesto de manifiesto la necesidad de proponer modelos socio-económicos alternativos que aúnen democracia, compromiso social y sostenibilidad del medio ambiente. La economía social y solidaria, sin ser un programa homogéneo, está contribuyendo a proponer respuestas a algunos de los problemas actuales en materia de desempleo e integración social, revalorizando en los procesos económicos, no sólo los intercambios mercantiles, sino también los intereses sociales y los recursos naturales. Abstract:This article aims to enlighten the importance ofsolidary and social economy in the present discussion, whose importance has increased as a result of the current economic crisis, making a special emphasis on subjects such as commons goods and democratic management. The crisis has brought up the need for alternative socio-economical management models which must combine democracy, social commitment and environmental sustainability. Solidary and social economy, without being a homogeneous program, are proposing answers to some of the present problems related to unemployment and social integration, contributing to increase the value of economic processes, not only in commercial exchanges, but also the social interest and natural resources. /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Tabla normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman";} /* Style Definitions */ table.MsoNormalTable {mso

  20. Bien-être des salariés et performance des magasins entrent-ils dans le même caddie?

    OpenAIRE

    Delobbe, Nathalie

    2012-01-01

    La protection du bien-être au travail est un droit des salariés. Mais peut-elle être aussi une composante essentielle de la performance des entreprises et un bénéfice pour l'employeur? Une enquête menée dans deux enseignes de la distribution belge a tenté de répondre à cette question.

  1. Fuentes de información para el diseño de un Sistema de Vigilancia e Inteligencia en el Registro Provincial de Bienes Culturales de Matanzas

    Directory of Open Access Journals (Sweden)

    Justa Bielka Cantillo González

    2007-01-01

    Full Text Available Por la importancia que reviste la conservación del Patrimonio Cultural, se identifican, con la utilización de herramientas estadísticas (Coeficiente de Concordancia de Kendall las fuentes de información relevantes, para el posterior diseño de un Sistema de Vigilancia e Inteligencia en el Registro Provincial de Bienes Culturales de la provincia de Matanzas

  2. El dominio público y los bienes públicos: Europa y América Latina. ¿El hijo sigue mirando al padre?

    Directory of Open Access Journals (Sweden)

    Sergio Chemás

    2015-12-01

    Full Text Available El estudio del derecho de los bienes públicos en América Latina y en Colombia es algo todavía poco desarrollado. Se sigue mirando hacia el derecho comparado para obtener respuestas, tal como un hijo mira a su padre, porque fue allá donde surgieron los grandes desarrollos del tema. El dominio público en Europa y América Latina es producto de un encuentro entre varias autoridades en el tema de los bienes públicos tanto de Europa como de América Latina. Esta reseña se divide en tres partes: i un breve análisis de derecho comparado frente al concepto de dominio público; ii la identificación de los contenidos más interesantes e innovadores de los regímenes de bienes públicos, y iii un ejercicio académico para que el lector lo desarrolle al leer el libro.

  3. Constructions from Dots and Lines

    CERN Document Server

    Rodriguez, Marko A

    2010-01-01

    A graph is a data structure composed of dots (i.e. vertices) and lines (i.e. edges). The dots and lines of a graph can be organized into intricate arrangements. The ability for a graph to denote objects and their relationships to one another allow for a surprisingly large number of things to be modeled as a graph. From the dependencies that link software packages to the wood beams that provide the framing to a house, most anything has a corresponding graph representation. However, just because it is possible to represent something as a graph does not necessarily mean that its graph representation will be useful. If a modeler can leverage the plethora of tools and algorithms that store and process graphs, then such a mapping is worthwhile. This article explores the world of graphs in computing and exposes situations in which graphical models are beneficial.

  4. Photoactivation of silicon quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Lockwood, R., E-mail: rossl@ualberta.c [Department of Physics, University of Alberta, Edmonton, Alberta, T6G 2G7 (Canada); McFarlane, S. [Department of Physics, University of Alberta, Edmonton, Alberta, T6G 2G7 (Canada); Rodriguez Nunez, J.R. [Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2 (Canada); Wang, X.Y. [Department of Physics, University of Alberta, Edmonton, Alberta, T6G 2G7 (Canada); Veinot, J.G.C. [Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2 (Canada); Meldrum, A. [Department of Physics, University of Alberta, Edmonton, Alberta, T6G 2G7 (Canada)

    2011-07-15

    We show that free-standing silicon quantum dots (QDs) can be photoactivated by blue or UV optical irradiation. The luminescence intensity increases by an order of magnitude for irradiation times of several minutes under moderate optical power. The cut-off energy for photoactivation is between 2.1 and 2.4 eV, not very different from the activation energy for hydrogen dissociation from bulk silicon surfaces. We propose the mechanism for this effect is associated with silicon-hydride bond breaking and the subsequent oxidation of dangling bonds. This phenomenon could be used to 'write' luminescent quantum dots into pre-determined arrays. - Research highlights: {yields}Laser light causes increased photoluminescence intensity in silicon quantum dots. {yields} The photoactivation process is effective for wavelengths of 514 nm and shorter. {yields} Hydrogen bound to the Si-QDs is replaced by oxygen in a two-step process. {yields} Patterning is possible but limited by physical dispersion of Si-QDs.

  5. Few-electron quantum dots

    International Nuclear Information System (INIS)

    We review some electron transport experiments on few-electron, vertical quantum dot devices. The measurement of current versus source-drain voltage and gate voltage is used as a spectroscopic tool to investigate the energy characteristics of interacting electrons confined to a small region in a semiconducting material. Three energy scales are distinguished: the single-particle states, which are discrete due to the confinement involved; the direct Coulomb interaction between electron charges on the dot; and the exchange interaction between electrons with parallel spins. To disentangle these energies, a magnetic field is used to reorganize the occupation of electrons over the single-particle states and to induce changes in the spin states. We discuss the interactions between small numbers of electrons (between 1 and 20) using the simplest possible models. Nevertheless, these models consistently describe a large set of experiments. Some of the observations resemble similar phenomena in atomic physics, such as shell structure and periodic table characteristics, Hund's rule, and spin singlet and triplet states. The experimental control, however, is much larger than for atoms: with one device all the artificial elements can be studied by adding electrons to the quantum dot when changing the gate voltage. (author)

  6. Charge State Hysteresis in Semiconductor Quantum Dots

    OpenAIRE

    Yang, C. H.; Rossi, A; Lai, N. S.; Leon, R.; Lim, W. H.; Dzurak, A.S.

    2014-01-01

    Semiconductor quantum dots provide a two-dimensional analogy for real atoms and show promise for the implementation of scalable quantum computers. Here, we investigate the charge configurations in a silicon metal-oxide-semiconductor double quantum dot tunnel coupled to a single reservoir of electrons. By operating the system in the few-electron regime, the stability diagram shows hysteretic tunnelling events that depend on the history of the dots charge occupancy. We present a model which acc...

  7. Resonant electron transfer between quantum dots

    OpenAIRE

    Openov, Leonid A.

    1999-01-01

    An interaction of electromagnetic field with a nanostructure composed of two quantum dots is studied theoretically. An effect of a resonant electron transfer between the localized low-lying states of quantum dots is predicted. A necessary condition for such an effect is the existence of an excited bound state whose energy lies close to the top of the barrier separating the quantum dots. This effect may be used to realize the reversible quantum logic gate NOT if the superposition of electron s...

  8. Optical Fiber Sensing Using Quantum Dots

    Directory of Open Access Journals (Sweden)

    Faramarz Farahi

    2007-12-01

    Full Text Available Recent advances in the application of semiconductor nanocrystals, or quantumdots, as biochemical sensors are reviewed. Quantum dots have unique optical properties thatmake them promising alternatives to traditional dyes in many luminescence basedbioanalytical techniques. An overview of the more relevant progresses in the application ofquantum dots as biochemical probes is addressed. Special focus will be given toconfigurations where the sensing dots are incorporated in solid membranes and immobilizedin optical fibers or planar waveguide platforms.

  9. Activation of silicon quantum dots for emission

    Institute of Scientific and Technical Information of China (English)

    Huang Wei-Qi; Miao Xin-Jian; Huang Zhong-Mei; Liu Shi-Rong; Qin Chao-Jian

    2012-01-01

    The emission of silicon quantum dots is weak when their surface is passivated well. Oxygen or nitrogen on the surface of silicon quantum dots can break the passivation to form localized electronic states in the band gap to generate active centers where stronger emission occurs.From this point of view,we can build up radiative matter for emission.Emissions of various wavelengths can be obtained by controlling the surface bonds of silicon quantum dots.Our experimental results demonstrate that annealing is important in the treatment of the activation,and stimulated emissions at about 600 and 700 nm take place on active silicon quantum dots.

  10. Thermoelectric energy harvesting with quantum dots.

    Science.gov (United States)

    Sothmann, Björn; Sánchez, Rafael; Jordan, Andrew N

    2015-01-21

    We review recent theoretical work on thermoelectric energy harvesting in multi-terminal quantum-dot setups. We first discuss several examples of nanoscale heat engines based on Coulomb-coupled conductors. In particular, we focus on quantum dots in the Coulomb-blockade regime, chaotic cavities and resonant tunneling through quantum dots and wells. We then turn toward quantum-dot heat engines that are driven by bosonic degrees of freedom such as phonons, magnons and microwave photons. These systems provide interesting connections to spin caloritronics and circuit quantum electrodynamics.

  11. POLARON IN CYLINDRICAL AND SPHERICAL QUANTUM DOTS

    Directory of Open Access Journals (Sweden)

    L.C.Fai

    2004-01-01

    Full Text Available Polaron states in cylindrical and spherical quantum dots with parabolic confinement potentials are investigated applying the Feynman variational principle. It is observed that for both kinds of quantum dots the polaron energy and mass increase with the increase of Frohlich electron-phonon coupling constant and confinement frequency. In the case of a spherical quantum dot, the polaron energy for the strong coupling is found to be greater than that of a cylindrical quantum dot. The energy and mass are found to be monotonically increasing functions of the coupling constant and the confinement frequency.

  12. Semiconductor quantum-dot lasers and amplifiers

    DEFF Research Database (Denmark)

    Hvam, Jørn Märcher; Borri, Paola; Ledentsov, N. N.;

    2002-01-01

    -power surface emitting VCSELs. We investigated the ultrafast dynamics of quantum-dot semiconductor optical amplifiers. The dephasing time at room temperature of the ground-state transition in semiconductor quantum dots is around 250 fs in an unbiased amplifier, decreasing to below 50 fs when the amplifier...... is biased to positive net gain. We have further measured gain recovery times in quantum dot amplifiers that are significantly lower than in bulk and quantum-well semiconductor optical amplifiers. This is promising for future demonstration of quantum dot devices with high modulation bandwidth...

  13. Quantum Dot Spectrum Converters for Enhanced High Efficiency Photovoltaics Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This research proposes to enhance solar cell efficiency, radiation resistance and affordability. The Quantum Dot Spectrum Converter (QDSC) disperses quantum dots...

  14. La Importancia del Grado de Intensidad de la Distribución en la Determinación del Valor de Marca de un Bien Duradero

    OpenAIRE

    Villarejo Ramos, Ángel Francisco

    2003-01-01

    En el presente trabajo pretendemos establecer una base teórica y empírica para la consideración de la influencia que ejerce el grado de intensidad con que es distribuido un bien duradero en la determinación del valor de marca de los mismos. Tras la revisión teórica que sustenta la posibilidad de aplicar técnicas de análisis basadas en los modelos de ecuaciones estructurales planteamos la confirmación empírica, en su caso, de las relaciones existentes entre la intensidad de la d...

  15. Sobre los saberes culturales y el fenómeno "sentirse bien-sentirse mal" On cultural knowledge and the phenomenon "feel good-fell bad"

    Directory of Open Access Journals (Sweden)

    Virtudes Rodero Sánchez

    2010-09-01

    Full Text Available El objetivo del presente estudio es identificar los saberes culturales inmersos en el fenómeno "sentirse-bien, sentirse mal", en diferentes situaciones de cuidado. Se elaboró un estudio cualitativo con un enfoque fenomenológico interpretativo, mediante el análisis de 18 narrativas a partir de entrevistas en profundidad realizadas por alumnas del Máster en Ciencias de la Enfermería en diferentes contextos de cuidados. Las categorías identificadas fueron: (1 Cronicidad y concepto de sentirse bien-sentirse mal. En la cronicidad este concepto está íntimamente relacionado con la recuperación de las actividades de la vida diaria y es componente importante en la percepción individual del concepto "calidad de vida". (2 Momentos agudos de enfermedad y concepto de sentirse bien-sentirse mal. En el análisis de los relatos del paciente aparecieron aspectos esenciales del fenómeno "sentirse bien-sentirse mal" para aumentar la comprensión de aspectos universales de algunos de sus componentes. Destacar que el fenómeno está íntimamente relacionado con la recuperación de las actividades de la vida diaria, y es un mediador importante en la percepción individual del concepto "calidad de vida". El interés de cara al cuidado es distinguir sus componentes universales, contextualizarlos en la práctica, dentro de las singularidades que presenta cada persona, de modo que nos permita su potenciación. El resultado es un cambio en la experiencia sentida.The object of the present study is to identify cultural knowledges immersed in the feeling-well, feeling-bad phenomenon in different care settings. A qualitative study was undertaken using a phenomenological interpretation approach through a meta-analysis of 18 narratives of profound interviews undertaken by Nursing Science Master Degree Students in different care situations. The categories established were: (1 Chronicity and the concept of feeling well-feeling bad. In this category, this concept is

  16. Composición de los hogares y niveles de gastos en bienes y servicios básicos en el departamento del cauca, Colombia

    OpenAIRE

    Andrés Mauricio Gómez Sánchez; Claudia Liceth Fajardo Hoyos; Juliana Isabel Sarmiento Castillo

    2016-01-01

    Éste documento tiene como objetivo caracterizar los hogares rurales y urbanos del departamento del Cauca, Colombia y clasificarlos según la tipología y el ciclo de vida del hogar, para establecer su relación con los niveles de gasto mínimo en bienes básicos, es decir, con los que definen los umbrales críticos de pobreza. Para tal efecto, se utiliza la Encuesta de Calidad de Vida de 2011 y se estiman modelos de análisis de varianza multifactoriales. Los resultados muestran, entre otros, que el...

  17. La doctrina de los bienes comunes de Francisco de Vitoria como fundamentación del dominio en el Nuevo Mundo

    OpenAIRE

    Añaños-Meza, M.C. (Mª Cecilia)

    2013-01-01

    En los últimos años se ha producido un renacimiento de la antigua idea de los bienes comunes como opción alternativa a las formas actuales de propiedad privada y pública, cuyos propulsores hacen referencia a su fuente más cierta, el derecho romano. Aunque es poco o nada conocido, esta idea fue empleada en el siglo XVI por el dominico español Francisco de Vitoria como una parte fundamental de su teoría del dominio que no sólo le va a servir para elaborar su análisis sob...

  18. Reestimación del grado de transmisión de la tasa de cambio del peso sobre la inflación de los bienes importados

    OpenAIRE

    2014-01-01

    Conocer el grado de transmisión de los cambios en la tasa de cambio sobre la inflación interna es un interrogante constante de las autoridades monetarias de cualquier país. En este documento se reestima el grado de transmisión de corto y mediano plazo de las variaciones de la tasa de cambio del peso colombiano sobre la inflación de los bienes importados, estimados en González et al. (2010). Se utilizan datos trimestrales de Colombia para el período 1985-2014 y un modelo VAR no lineal de trans...

  19. Perspectivas del crecimiento urbano: la actividad comercial minorista y el transporte de bienes en la Zona Metropolitana de Querétaro (México)

    OpenAIRE

    Eduardo Betanzo-Quezada

    2015-01-01

    Se muestran las perspectivas del crecimiento urbano, la actividad comercial minorista y su relación transversal con el transporte de bienes en la Zona Metropolitana de Querétaro (México). Con una metodología de análisis de información estadística de tipo agregado, se examinan esos determinantes con el objetivo de revelar sus tendencias en la ciudad. El paralelismo encontrado en las tendencias de comportamiento de los determinantes examinados conduce a concluir que es cada vez más necesario co...

  20. Economía del bien común y los DESC en la enseñanza del derecho constitucional

    OpenAIRE

    Garay Montañez, Nilda

    2013-01-01

    El presente es un trabajo que resulta de la aplicación de los principios básicos de la Economía del Bien Común en las clases de derecho constitucional. Principios que tienen estrecha relación con los denominados DESC: Derechos Económicos Sociales y Culturales que han venido desarrollándose en las sociedades donde el nivel de la pobreza es alto, es decir, los Estados de la región denominada de la periferia. Los Estados constitucionales occidentales han construido amplia doctrina al respecto, p...

  1. Los bienes de capital en el Programa de Cooperación e Integración Argentina-Brasil : 1986-1989

    OpenAIRE

    Luchetti, Javier Fernando

    2005-01-01

    El MERCOSUR es constituido como una continuidad del Programa de Integración y Cooperación entre Argentina y Brasil, si bien abandona sus principios fundamentales, cambiando sensiblemente su diseño global y el modelo de integración subyacente. El PICAB se proponía crear un espacio económico común para mejorar el bienestar de los pueblos, mediante una complementación de sectores de las economías de ambos países, según los principios de gradualismo, flexibilidad, selectividad, equilibrio, profun...

  2. La protección del “paisaje sonoro”: Los toques manuales de campanas y su declaración como Bien de Interés Cultural

    Directory of Open Access Journals (Sweden)

    Francisca Ramón Fernández

    2014-06-01

    Full Text Available En el presente trabajo analizamos la protección de los toques manuales de campanas y su declaración como Bien de Interés Cultural Inmaterial por parte de la legislación de patrimonio cultural valenciano. A través de la evolución histórica del bien podemos observar las razones de su protección y nos ha llevado a cuestionarnos si ha sido adecuado su consideración como paisaje sonoro, concepto muy alejado en el ámbito jurídico y que no es compartido plenamente. Siendo la primera vez que se protege este bien, resulta especialmente interesante la ampliación de la protección a los denominados elementos que forman parte del bien, como es el caso de las partituras.

  3. Quantum Gates Between Two Spins in a Triple Dot System with an Empty Dot

    CERN Document Server

    Coello, Jose Garcia

    2011-01-01

    We propose a scheme for implementing quantum gates and entanglement between spin qubits in the outer dots of a triple-dot system with an empty central dot. The voltage applied to the central dot can be tuned to realize the gate. Our scheme exemplifies the possibility of quantum gates outside the regime where each dot has an electron, so that spin-spin exchange interaction is not the only relevant mechanism. Analytic treatment is possible by mapping the problem to a t-J model. The fidelity of the entangling quantum gate between the spins is analyzed in the presence of decoherence stemming from a bath of nuclear spins, as well as from charge fluctuations. Our scheme provides an avenue for extending the scope of two qubit gate experiments to triple-dots, while requiring minimal control, namely that of the potential of a single dot, and may enhance the qubit separation to ease differential addressability.

  4. Nitrogen-Doped Carbon Dots for "green" Quantum Dot Solar Cells.

    Science.gov (United States)

    Wang, Hao; Sun, Pengfei; Cong, Shan; Wu, Jiang; Gao, Lijun; Wang, Yun; Dai, Xiao; Yi, Qinghua; Zou, Guifu

    2016-12-01

    Considering the environment protection, "green" materials are increasingly explored for photovoltaics. Here, we developed a kind of quantum dots solar cell based on nitrogen-doped carbon dots. The nitrogen-doped carbon dots were prepared by direct pyrolysis of citric acid and ammonia. The nitrogen-doped carbon dots' excitonic absorption depends on the N-doping content in the carbon dots. The N-doping can be readily modified by the mass ratio of reactants. The constructed "green" nitrogen-doped carbon dots solar cell achieves the best power conversion efficiency of 0.79 % under AM 1.5 G one full sun illumination, which is the highest efficiency for carbon dot-based solar cells. PMID:26781285

  5. Photoinduced electron transfers with carbon dots

    OpenAIRE

    Wang, Xin; Cao, Li; Lu, Fushen; Meziani, Mohammed J.; Li, Heting; Qi, Gang; Zhou, Bing; Harruff, Barbara A.; Kermarrec, Fabien; Sun, Ya-Ping

    2009-01-01

    The photoluminescence in carbon dots (surface-passivated small carbon nanoparticles) could be quenched efficiently by electron acceptor or donor molecules in solution, namely that photo-excited carbon dots are both excellent electron donors and excellent electron acceptors, thus offering new opportunities for their potential uses in light energy conversion and related applications.

  6. Thick-shell nanocrystal quantum dots

    Science.gov (United States)

    Hollingsworth, Jennifer A.; Chen, Yongfen; Klimov, Victor I.; Htoon, Han; Vela, Javier

    2011-05-03

    Colloidal nanocrystal quantum dots comprising an inner core having an average diameter of at least 1.5 nm and an outer shell, where said outer shell comprises multiple monolayers, wherein at least 30% of the quantum dots have an on-time fraction of 0.80 or greater under continuous excitation conditions for a period of time of at least 10 minutes.

  7. Optical Properties of Semiconductor Quantum Dots

    NARCIS (Netherlands)

    Perinetti, U.

    2011-01-01

    This thesis presents different optical experiments performed on semiconductor quantum dots. These structures allow to confine a small number of electrons and holes to a tiny region of space, some nm across. The aim of this work was to study the basic properties of different types of quantum dots mad

  8. Detecting the chirality for coupled quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Cao Huijuan [Institute for Condensed Matter Physics, School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510631 (China); Hu Lian [Institute for Condensed Matter Physics, School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510631 (China)], E-mail: huliancaohj@yahoo.com

    2008-04-21

    We propose a scheme to detect the chirality for a system consisting of three coupled quantum dots. The chirality is found to be determined by the frequency of the transition between chiral states under the chiral symmetry broken perturbation. The results are important to construct quantum gates and to demonstrate chiral entangle states in the triangle spin dots.

  9. Double Acceptor Interaction in Semimagnetic Quantum Dot

    Directory of Open Access Journals (Sweden)

    A. Merwyn Jasper D. Reuben

    2011-01-01

    Full Text Available The effect of geometry of the semimagnetic Quantum Dot on the Interaction energy of a double acceptor is computed in the effective mass approximation using the variational principle. A peak is observed at the lower dot sizes as a magnetic field is increased which is attributed to the reduction in confinement.

  10. Model-based clustered-dot screening

    Science.gov (United States)

    Kim, Sang Ho

    2006-01-01

    I propose a halftone screen design method based on a human visual system model and the characteristics of the electro-photographic (EP) printer engine. Generally, screen design methods based on human visual models produce dispersed-dot type screens while design methods considering EP printer characteristics generate clustered-dot type screens. In this paper, I propose a cost function balancing the conflicting characteristics of the human visual system and the printer. By minimizing the obtained cost function, I design a model-based clustered-dot screen using a modified direct binary search algorithm. Experimental results demonstrate the superior quality of the model-based clustered-dot screen compared to a conventional clustered-dot screen.

  11. Substitutional impurity in the graphene quantum dots

    Science.gov (United States)

    Sierański, K.; Szatkowski, J.

    2015-09-01

    The process of formation of the localized defect states due to substitutional impurity in sp2-bonded graphene quantum dot is considered using a simple tight-binding-type calculation. We took into account the interaction of the quantum dot atoms surrounding the substitutional impurity from the second row of elements. To saturate the external dangling sp2 orbitals of the carbon additionally 18 hydrogen atoms were introduced. The chemical formula of the quantum dot is H18C51X, where X is the symbol of substitutional atom. The position of the localized levels is determined relative to the host-atoms (C) εp energies. We focused on the effect of substitutional doping by the B, N and O on the eigenstate energies and on the total energy change of the graphene dots including for O the effect of lattice distorsion. We conclude that B, N, and O can form stable substitutional defects in graphene quantum dot.

  12. Synthèse et propriétés optiques de quantum dots fluorescents plasmoniques

    OpenAIRE

    Ji, Botao

    2014-01-01

    Grâce aux plasmons de surface des nanoparticules métalliques et aux propriétés optiques et électroniques exceptionnelles des quantum dots (QDs), les nanostructures hybrides QD/métal ont suscité beaucoup d'intérêt depuis une dizaine d'années en raison de leurs nombreuses applications potentielles. Cependant, les hybrides QD/or colloïdaux n'ont été que rarement obtenus bien que ces structures soient particulièrement prometteuses du point de vue optique et qu'elles puissent être manipulées très ...

  13. La casa y el ajuar de la familia Coronel a través de un inventario de bienes del siglo XVI

    Directory of Open Access Journals (Sweden)

    De la Peña Barroso, Efrén

    2015-12-01

    Full Text Available In the last years we have been working on the person of don Abraham Seneor/Fernán Pérez Coronel and his offspring, mainly from his son Íñigo López Coronel. In this occasion we will focus on the structure of the dwelling house and the household goods of the family through an inventory made in Segovia in 1522. This document will allow us to know the wealth level, the shy investment in luxury goods and the list of part of the household goods of this important family of Segovian conversos.Desde hace ya varios años estamos trabajando en la figura de don Abraham Seneor/Fernán Pérez Coronel y su descendencia, sobre todo por la vía de su hijo Íñigo López Coronel. En esta ocasión, estudiaremos la estructura espacial de su casa, sus bienes muebles y el ajuar de esta rama familiar a través de un inventario de bienes realizado en sus «casas principales» de la ciudad de Segovia en el año 1522. Este inventario nos permitirá acercarnos a los niveles de riqueza, a la escasa inversión en productos de lujo y al conocimiento de gran parte del ajuar de esta importante familia de judeoconversos segovianos.

  14. La repercusión del valor razonable de los bienes inmuebles en la utilidad de los estados financieros: una nota de investigación

    Directory of Open Access Journals (Sweden)

    Andrés Navarro Galera

    2009-01-01

    Full Text Available La elección en la reciente reforma contable española del criterio de valor razonable en lugar del coste histórico como base de valoración para determinados activos ha generado cierta controversia. Este trabajo estudia la posible incidencia de la adopción del valor razonable para el registro contable de los bienes inmuebles sobre la relevancia y la fiabilidad de la información financiera. El estudio empírico está basado en una encuesta sobre las percepciones de 151 responsables de la contabilidad de empresas españolas del sector de la construcción sobre la utilidad y fiabilidad de la información financiera basada en el valor razonable. El análisis de los resultados nos ha permitido concluir que, respecto al coste histórico, los responsables de contabilidad perciben que el valor razonable de los bienes inmuebles generaría estados financieros más útiles para representar la imagen fiel del patrimonio de la empresa. No obstante, los encuestados conciben la información financiera bajo valor razonable como menos objetiva y verificable. Asimismo, hemos comprobado que el tamaño de la empresa puede influir en la opinión de la repercusión del valor razonable sobre la relevancia y fiabilidad de los estados financieros.

  15. Electron transport in quantum dots

    CERN Document Server

    2003-01-01

    When I was contacted by Kluwer Academic Publishers in the Fall of 200 I, inviting me to edit a volume of papers on the issue of electron transport in quantum dots, I was excited by what I saw as an ideal opportunity to provide an overview of a field of research that has made significant contributions in recent years, both to our understanding of fundamental physics, and to the development of novel nanoelectronic technologies. The need for such a volume seemed to be made more pressing by the fact that few comprehensive reviews of this topic have appeared in the literature, in spite of the vast activity in this area over the course of the last decade or so. With this motivation, I set out to try to compile a volume that would fairly reflect the wide range of opinions that has emerged in the study of electron transport in quantum dots. Indeed, there has been no effort on my part to ensure any consistency between the different chapters, since I would prefer that this volume instead serve as a useful forum for the...

  16. Quantum Dots Investigated for Solar Cells

    Science.gov (United States)

    Bailey, Sheila G.; Castro, Stephanie L.; Raffaelle, Ryne P.; Hepp, Aloysius F.

    2001-01-01

    The NASA Glenn Research Center has been investigating the synthesis of quantum dots of CdSe and CuInS2 for use in intermediate-bandgap solar cells. Using quantum dots in a solar cell to create an intermediate band will allow the harvesting of a much larger portion of the available solar spectrum. Theoretical studies predict a potential efficiency of 63.2 percent, which is approximately a factor of 2 better than any state-of-the-art devices available today. This technology is also applicable to thin-film devices--where it offers a potential four-fold increase in power-to-weight ratio over the state of the art. Intermediate-bandgap solar cells require that quantum dots be sandwiched in an intrinsic region between the photovoltaic solar cell's ordinary p- and n-type regions (see the preceding figure). The quantum dots form the intermediate band of discrete states that allow sub-bandgap energies to be absorbed. However, when the current is extracted, it is limited by the bandgap, not the individual photon energies. The energy states of the quantum dot can be controlled by controlling the size of the dot. Ironically, the ground-state energy levels are inversely proportional to the size of the quantum dots. We have prepared a variety of quantum dots using the typical organometallic synthesis routes pioneered by Ba Wendi et al., in the early 1990's. The most studied quantum dots prepared by this method have been of CdSe. To produce these dots, researchers inject a syringe of the desired organometallic precursors into heated triocytlphosphine oxide (TOPO) that has been vigorously stirred under an inert atmosphere (see the following figure). The solution immediately begins to change from colorless to yellow, then orange and red/brown, as the quantum dots increase in size. When the desired size is reached, the heat is removed from the flask. Quantum dots of different sizes can be identified by placing them under a "black light" and observing the various color differences in

  17. Fluorescent Quantum Dots for Biological Labeling

    Science.gov (United States)

    McDonald, Gene; Nadeau, Jay; Nealson, Kenneth; Storrie-Lomardi, Michael; Bhartia, Rohit

    2003-01-01

    Fluorescent semiconductor quantum dots that can serve as "on/off" labels for bacteria and other living cells are undergoing development. The "on/off" characterization of these quantum dots refers to the fact that, when properly designed and manufactured, they do not fluoresce until and unless they come into contact with viable cells of biological species that one seeks to detect. In comparison with prior fluorescence-based means of detecting biological species, fluorescent quantum dots show promise for greater speed, less complexity, greater sensitivity, and greater selectivity for species of interest. There are numerous potential applications in medicine, environmental monitoring, and detection of bioterrorism.

  18. Time-bin Entanglement from Quantum Dots

    CERN Document Server

    Weihs, Gregor; Predojević, Ana

    2016-01-01

    The desire to have a source of single entangled photon pairs can be satisfied using single quantum dots as emitters. However, we are not bound to pursue only polarization entanglement, but can also exploit other degrees of freedom. In this chapter we focus on the time degree of freedom, to achieve so-called time-bin entanglement. This requires that we prepare the quantum dot coherently into the biexciton state and also build special interferometers for analysis. Finally this technique can be extended to achieve time-bin and polarization hyper-entanglement from a suitable quantum dot.

  19. Achats de biens et services des organisations internationales dans les pays industrialisés et les économies émergentes

    Directory of Open Access Journals (Sweden)

    Gilles Carbonnier

    2013-08-01

    Full Text Available Cet article examine l’évolution des achats de biens et services des organisations multilatérales auprès de fournisseurs établis dans les pays industrialisés et les économies émergentes. Il présente les résultats d’une étude empirique – première du genre – sur les facteurs explicatifs des inégalités entre pays. Les différences s’expliquent notamment par la force du secteur manufacturier et les relations d’affaires établies dans le passé. Les résultats laissent penser que les contributions versées par les pays donateurs peuvent avoir une influence positive sur les achats de biens et services, nonobstant le fait que les organisations multilatérales recourent à des procédures d’appels d’offres internationaux. La proximité géographique, les affinités culturelles et linguistiques et la présence dans le pays du siège d’une organisation multilatérale jouent également un rôle positif. Les achats de biens et services des agences multilatérales peuvent être considérés comme une retombée indirecte de l’aide publique au développement (APD. Alors que nombre d’entre eux font face à de sérieuses difficultés économiques et contraintes budgétaires, documenter un tel « retour sur investissement » peut contribuer à convaincre les décideurs politiques d’augmenter – ou simplement de ne pas réduire – les budgets d’APD. De tels arguments doivent toutefois demeurer marginaux par rapport aux questions centrales de la pertinence et l’efficacité de l’aide, et des performances des organisations multilatérales.

  20. Producción y percepción de bienes públicos en la lógica de la acción colectiva

    Directory of Open Access Journals (Sweden)

    Jordana, Jacint

    2007-04-01

    Full Text Available Public goods having different proprieties produce different problems of collective action. This hypothesis has been discussed from different analytical perspectives and we examine their arguments, aiming to deepen our theoretical understanding about the logic of collective action. In this paper we look for similarities and differences regarding their use of concepts and expected results. Simultaneously, we examine the link between different public goods and the interdependent behavior of individuals. To this purpose, we also revisit the connections between production functions and consumption types in the case of public goods, as a mean to explore the potential development of more elaborated models in the theory of collective action, and suggest that more empirical contrast of these models is needed. Finally, we argue the importance for theoretical discussions to include a discussion about the impact of perception in the collective action models, considering systematic deviations to rational choice, and conclude that no single theory may address all collective action problems, but systematic patterns of behavior may be identified and empirically confirmed.

    Bienes públicos con distintas propiedades generan problemas diferentes de acción colectiva. Esta hipótesis ha sido discutida, desde distintas perspectivas analíticas, con el objeto de profundizar teóricamente sobre la lógica de la acción colectiva. En este trabajo se revisan las aportaciones recientes a esta cuestión, analizando sus puntos de encuentro y sus divergencias en cuanto a conceptos y resultados esperados. Asimismo, se examina la relación entre tipos distintos de bienes públicos y el comportamiento interdependiente de los individuos. Con este fin, los vínculos entre las funciones de producción y las formas de consumo de bienes públicos también son considerados, ya que permite desarrollar modelos más ambiciosos sobre la lógica de la acción colectiva. Finalmente

  1. Perspectivas del crecimiento urbano: la actividad comercial minorista y el transporte de bienes en la Zona Metropolitana de Querétaro (México

    Directory of Open Access Journals (Sweden)

    Eduardo Betanzo-Quezada

    2015-01-01

    Full Text Available Se muestran las perspectivas del crecimiento urbano, la actividad comercial minorista y su relación transversal con el transporte de bienes en la Zona Metropolitana de Querétaro (México. Con una metodología de análisis de información estadística de tipo agregado, se examinan esos determinantes con el objetivo de revelar sus tendencias en la ciudad. El paralelismo encontrado en las tendencias de comportamiento de los determinantes examinados conduce a concluir que es cada vez más necesario conectar al transporte urbano de carga con la planeación económica y urbana, y ubicarlo dentro de las prioridades de las administraciones gubernamentales.

  2. ¿Cómo acercar los bienes patrimoniales a los ciudadanos? Educación Patrimonial, un campo emergente en la gestión del patrimonio cultural

    Directory of Open Access Journals (Sweden)

    Zaida García Valecillo

    2009-01-01

    Lamentablemente en las sociedades contemporáneas éste se aleja de la memoria de los ciudadanos. Por ello la gestión patrimonial busca la participación de los actores sociales, en donde la Educación Patrimonial puede ser una herramienta importante en este proceso. Esto implica desarrollar bases teóricas y metodológicas específicas que involucren a los ciudadanos en la sustentabilidad de las comunidades y sus bienes patrimoniales. En tal sentido, proponemos analizar la educación patrimonial como un campo emergente, a través de cuatro dimensiones pedagógicas que permitan sistematizar sus alcances y estrategias. Para luego articular dichas dimensiones en tres áreas de actuación educativa.

  3. Large quantum dots with small oscillator strength

    DEFF Research Database (Denmark)

    Stobbe, Søren; Schlereth, T.W.; Höfling, S.;

    2010-01-01

    We have measured the oscillator strength and quantum efficiency of excitons confined in large InGaAs quantum dots by recording the spontaneous emission decay rate while systematically varying the distance between the quantum dots and a semiconductor-air interface. The size of the quantum dots...... is measured by in-plane transmission electron microscopy and we find average in-plane diameters of 40 nm. We have calculated the oscillator strength of excitons of that size assuming a quantum-dot confinement given by a parabolic in-plane potential and a hard-wall vertical potential and predict a very large...... oscillator strength due to Coulomb effects. This is in stark contrast to the measured oscillator strength, which turns out to be so small that it can be described by excitons in the strong confinement regime. We attribute these findings to exciton localization in local potential minima arising from alloy...

  4. Ge Quantum Dot Infrared Imaging Camera Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Luna Innovations Incorporated proposes to develop a high performance Ge quantum dots-based infrared (IR) imaging camera on Si substrate. The high sensitivity, large...

  5. Spin current in double quantum dot

    Institute of Scientific and Technical Information of China (English)

    Zhao Hua; Zhang Guo-Feng; Yin Wen; Liang Jiu-Qing

    2004-01-01

    We have studied the dynamical behaviours of two electrons confined in a double quantum dot driven by rotating magnetic fields in terms of the theory of Lewis-Riesenfeld Hermitian invariants for the explicitly time-dependent Hamiltonian. The coherent spin oscillations in the dot provide a generation source for spin current. Exact solutions obtained allow us to investigate the dynamical properties of the spin localization for various initial localized states.

  6. Magnetic quantum dots and magnetic edge states

    International Nuclear Information System (INIS)

    Starting with defining the magnetic edge state in a magnetic quantum dot, which becomes quite popular nowadays conjunction with a possible candidate for a high density memory device or spintronic materials, various magnetic nano-quantum structures are reviewed in detail. We study the magnetic edge states of the two dimensional electron gas in strong perpendicular magnetic fields. We find that magnetic edge states are formed along the boundary of the magnetic dot, which is formed by a nonuniform distribution of magnetic fields. These magnetic edge states circulate either clockwise or counterclockwise, depending on the number of missing flux quanta, and exhibit quite different properties, as compared to the conventional ones which are induced by electrostatic confinements in the quantum Hall system. We also find that a close relation between the quantum mechanical eigenstates and the classical trajectories in the magnetic dot. When a magnetic dot is located inside a quantum wire, the edge-channel scattering mechanism by the magnetic quantum dot is very different from that by electrostatic dots. Here, the magnetic dot is formed by two different magnetic fields inside and outside the dot. We study the ballistic edge-channel transport and magnetic edge states in this situation. When the inner field is parallel to the outer one, the two-terminal conductance is quantized and shows the features of a transmission barrier and a resonator. On the other hand, when the inner field is reversed, the conductance is not quantized and all channels can be completely reflected in some energy ranges. The difference between the above two cases results from the distinct magnetic confinements. We also describe successfully the edge states of magnetic quantum rings and others in detail

  7. Coherent scattering in a small quantum dot

    International Nuclear Information System (INIS)

    Ballistic transport in an open small (100 nm) three-terminal quantum dot based on the high-mobility two-dimensional electron gas of the AlGaAs/GaAs heterojunction has been analyzed. It has been shown that the gate oscillations of resistance of such a dot arise due to the coherent scattering of electrons on its quasidiscrete levels being suppressed by a weak magnetic field

  8. Exploring Extragalactic Emission: The Hα Dot Survey

    Science.gov (United States)

    Rampalli, Rayna; Salzer, John Joseph

    2016-01-01

    The Hα Dot Survey was established as a result of finding point sources of strong line emission in the data obtained for the ALFALFA Hα Survey (Van Sistine et al. 2015). In the latter survey, broad-band R and narrow-band Hα filters were used to examine target galaxies from the ALFALFA blind HI survey (Giovanelli et al. 2005, Haynes et al. 2011). In the process of reducing the ALFALFA Hα Survey data the "Hα Dots" were discovered (Kellar et al. 2008, 2012). Using specialized image analysis tools, a large population of dots has already been detected in the more than 1500 ALFALFA Hα narrow-band images taken with the 0.9m WIYN and 2.1m KPNO telescopes. Follow-up spectra of over 200 Hα Dots discovered from the 0.9m images reveal that these objects are a mix of nearby low-luminosity star-forming galaxies, compact starbursts and Seyfert 2 galaxies at intermediate redshifts, and high-redshift QSOs. Here we present the first list of Hα Dots detected using 2.1m telescope data. The 2.1m images yield a sample of Dots that average almost two magnitudes fainter than those detected with the 0.9m. The current REU project is designed to characterize the set of Hα Dots detected in the deeper 2.1m telescope images, while the broad goals of the Hα Dot Survey include the desire to understand better the chemical evolution of galaxies over cosmic time. This project was supported in part by the NSF REU grant 1358980, by the Maria Mitchell Association (Nantucket, MA), and by the Massachusetts Space Grant Consortium.

  9. Formation and ordering of epitaxial quantum dots

    Science.gov (United States)

    Atkinson, Paola; Schmidt, Oliver G.; Bremner, Stephen P.; Ritchie, David A.

    2008-10-01

    Single quantum dots (QDs) have great potential as building blocks for quantum information processing devices. However, one of the major difficulties in the fabrication of such devices is the placement of a single dot at a pre-determined position in the device structure, for example, in the centre of a photonic cavity. In this article we review some recent investigations in the site-controlled growth of InAs QDs on GaAs by molecular beam epitaxy. The method we use is ex-situ patterning of the GaAs substrate by electron beam lithography and conventional wet or dry etching techniques to form shallow pits in the surface which then determine the nucleation site of an InAs dot. This method is easily scalable and can be incorporated with marker structures to enable simple post-growth lithographic alignment of devices to each site-controlled dot. We demonstrate good site-control for arrays with up to 10 micron spacing between patterned sites, with no dots nucleating between the sites. We discuss the mechanism and the effect of pattern size, InAs deposition amount and growth conditions on this site-control method. Finally we discuss the photoluminescence from these dots and highlight the remaining challenges for this technique. To cite this article: P. Atkinson et al., C. R. Physique 9 (2008).

  10. Quantum-dot-in-perovskite solids

    KAUST Repository

    Ning, Zhijun

    2015-07-15

    © 2015 Macmillan Publishers Limited. All rights reserved. Heteroepitaxy - atomically aligned growth of a crystalline film atop a different crystalline substrate - is the basis of electrically driven lasers, multijunction solar cells, and blue-light-emitting diodes. Crystalline coherence is preserved even when atomic identity is modulated, a fact that is the critical enabler of quantum wells, wires, and dots. The interfacial quality achieved as a result of heteroepitaxial growth allows new combinations of materials with complementary properties, which enables the design and realization of functionalities that are not available in the single-phase constituents. Here we show that organohalide perovskites and preformed colloidal quantum dots, combined in the solution phase, produce epitaxially aligned \\'dots-in-a-matrix\\' crystals. Using transmission electron microscopy and electron diffraction, we reveal heterocrystals as large as about 60 nanometres and containing at least 20 mutually aligned dots that inherit the crystalline orientation of the perovskite matrix. The heterocrystals exhibit remarkable optoelectronic properties that are traceable to their atom-scale crystalline coherence: photoelectrons and holes generated in the larger-bandgap perovskites are transferred with 80% efficiency to become excitons in the quantum dot nanocrystals, which exploit the excellent photocarrier diffusion of perovskites to produce bright-light emission from infrared-bandgap quantum-tuned materials. By combining the electrical transport properties of the perovskite matrix with the high radiative efficiency of the quantum dots, we engineer a new platform to advance solution-processed infrared optoelectronics.

  11. Coherent transport through interacting quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Hiltscher, Bastian

    2012-10-05

    The present thesis is composed of four different works. All deal with coherent transport through interacting quantum dots, which are tunnel-coupled to external leads. There a two main motivations for the use of quantum dots. First, they are an ideal device to study the influence of strong Coulomb repulsion, and second, their discrete energy levels can easily be tuned by external gate electrodes to create different transport regimes. The expression of coherence includes a very wide range of physical correlations and, therefore, the four works are basically independent of each other. Before motivating and introducing the different works in more detail, we remark that in all works a diagrammatic real-time perturbation theory is used. The fermionic degrees of freedom of the leads are traced out and the elements of the resulting reduced density matrix can be treated explicitly by means of a generalized master equation. How this equation is solved, depends on the details of the problem under consideration. In the first of the four works adiabatic pumping through an Aharonov-Bohm interferometer with a quantum dot embedded in each of the two arms is studied. In adiabatic pumping transport is generated by varying two system parameters periodically in time. We consider the two dot levels to be these two pumping parameters. Since they are located in different arms of the interferometer, pumping is a quantum mechanical effect purely relying on coherent superpositions of the dot states. It is very challenging to identify a quantum pumping mechanism in experiments, because a capacitive coupling of the gate electrodes to the leads may yield an undesired AC bias voltage, which is rectified by a time dependent conductance. Therefore, distinguishing features of these two transport mechanisms are required. We find that the dependence on the magnetic field is the key feature. While the pumped charge is an odd function of the magnetic flux, the rectified current is even, at least in

  12. Dot-dye-immunoassay for the diagnosis of schistosomiasis mansoni

    Directory of Open Access Journals (Sweden)

    Ana Lúcia Teles Rabello

    1992-06-01

    Full Text Available A new serological assay dot-dye-immunoassay (dot-DIA was evaluated for the diagnosis of schistosomiasis mansoni. This method consist of four steps: (a biding of antigens to a nitrocellulose membrane (NC; (b blocking of free sites of the NC; (c incubation in specific primary antibody; (d detection of primary antibody reactivity by color development using second antibody coupled to textile dyes. Sera from 82 individuals, 61 with Schistosoma mansoni eggs in the stool and 21 stool negative were tested by ELISA, dot-ELISA, and dotDIA. A high level of agreement between the methods tested was observed for all sera tested: ELISA x dot-ELISA: 95.1%, ELISA x dot-DIA: 92.7% and dot-ELISA x dot-DIA: 97.6%. In this study, dot-DIA proved to be a feasible, sensitive, rapid and practical test for the diagnosis of shcistosomiasis.

  13. ¿qué papel juega la definición de la eudaimonía en la concepción del bien humano de aristóteles?

    OpenAIRE

    Velásquez, Beatríz Alejandra

    2012-01-01

    Aristóteles propone una concepción del bien humano que determina (hasta con un cierto grado de precisión) cómo hemos de ser, actuar y en general vivir. Tal concepción se logra, según él, definiendo el bien humano, y en EN 1.7 lo define como “una actividad del alma según la virtud”. Esta definición no brinda información acerca de cómo ser y actuar, por lo que parece no contener la concepción esperada del bien, lo cual sí logra la teoría de la virtud presentada en libros posteriores. ¿Qué papel...

  14. Realistic model of a vertical pillar quantum dot: Analysis of individual dot data

    NARCIS (Netherlands)

    Maksym, P.A.; Nishi, Y.; Austing, D.G.; Hatano, T.; Kouwenhoven, L.P.; Aoki, H.; Tarucha, S.

    2009-01-01

    An accurate model of a vertical pillar quantum dot is described. The full three-dimensional structure of the device containing the dot is taken into account and this leads to an effective two-dimensional model in which electrons move in the two lateral dimensions, the confinement is parabolic, and t

  15. Submonolayer Quantum Dot Infrared Photodetector

    Science.gov (United States)

    Ting, David Z.; Bandara, Sumith V.; Gunapala, Sarath D.; Chang, Yia-Chang

    2010-01-01

    A method has been developed for inserting submonolayer (SML) quantum dots (QDs) or SML QD stacks, instead of conventional Stranski-Krastanov (S-K) QDs, into the active region of intersubband photodetectors. A typical configuration would be InAs SML QDs embedded in thin layers of GaAs, surrounded by AlGaAs barriers. Here, the GaAs and the AlGaAs have nearly the same lattice constant, while InAs has a larger lattice constant. In QD infrared photodetector, the important quantization directions are in the plane perpendicular to the normal incidence radiation. In-plane quantization is what enables the absorption of normal incidence radiation. The height of the S-K QD controls the positions of the quantized energy levels, but is not critically important to the desired normal incidence absorption properties. The SML QD or SML QD stack configurations give more control of the structure grown, retains normal incidence absorption properties, and decreases the strain build-up to allow thicker active layers for higher quantum efficiency.

  16. Understanding electronic systems in semiconductor quantum dots

    Science.gov (United States)

    Ciftja, Orion

    2013-11-01

    Systems of confined electrons are found everywhere in nature in the form of atoms where the orbiting electrons are confined by the Coulomb attraction of the nucleus. Advancement of nanotechnology has, however, provided us with an alternative way to confine electrons by using artificial confining potentials. A typical structure of this nature is the quantum dot, a nanoscale system which consists of few confined electrons. There are many types of quantum dots ranging from self-assembled to miniaturized semiconductor quantum dots. In this work we are interested in electrostatically confined semiconductor quantum dot systems where the electrostatic confining potential that traps the electrons is generated by external electrodes, doping, strain or other factors. A large number of semiconductor quantum dots of this type are fabricated by applying lithographically patterned gate electrodes or by etching on two-dimensional electron gases in semiconductor heterostructures. Because of this, the whole structure can be treated as a confined two-dimensional electron system. Quantum confinement profoundly affects the way in which electrons interact with each other, and external parameters such as a magnetic field. Since a magnetic field affects both the orbital and the spin motion of the electrons, the interplay between quantum confinement, electron-electron correlation effects and the magnetic field gives rise to very interesting physical phenomena. Thus, confined systems of electrons in a semiconductor quantum dot represent a unique opportunity to study fundamental quantum theories in a controllable atomic-like setup. In this work, we describe some common theoretical models which are used to study confined systems of electrons in a two-dimensional semiconductor quantum dot. The main emphasis of the work is to draw attention to important physical phenomena that arise in confined two-dimensional electron systems under various quantum regimes.

  17. Ciencia prohibida... ciencia buscada (A propósito de La ciencia del bien y del mal de Javier Echeverría

    Directory of Open Access Journals (Sweden)

    Gómez Pin, Víctor

    2007-06-01

    Full Text Available A labyrinth was the infinite for Leibniz (who declares on several occasions that,as much from the angle of the infinite large as from that of the infinite small, infinity is nothing but a fiction in the attempts of thought to explain the phenomena. But another labyrinth was also for him the problem of the evilness, together with the correlative problem of goodness. Used, since he was a young mathematician, to the Leibnizian puzzle of the infinite, Javier Echeverría faces now the second labyrinth. And he approaches the subject by restoring the biblical myth of the tree that hides the mystery. Taken implicitly the opposite point of view that leads Kant to assert the intrinsic division of the reason, Echeverría, from the very title of his book, aims at goodness and evilness as effective goals for science. In this paper we discuss some implications of Echeverría’s bet.

    Un laberinto era el infinito para Leibniz (quien afirma en varias ocasiones que tanto lo infinitamente grande como lo infinitamente pequeño no son sino ficciones para el pensamiento que busca la explicación de los fenómenos pero laberinto era asimismo, para él, la cuestión del mal, indisociable de problema del bien. Curtido, desde sus años de joven matemático, en el leibniziano puzzle del infinito y el continuo, Javier Echeverría se confronta ahora al segundo laberinto. Y lo hace restaurando el bíblico relato del árbol cuyo fruto escondería el misterio. Tomando implícitamente una vía opuesta a la que conduce a la kantiana división de la razón, Echeverría apunta a hacer de la polaridad bien-mal objeto de efectiva ciencia. En este escrito discutimos alguna de las implicaciones de su apuesta.

  18. La Repercusión del Valor Razonable de los Bienes Inmuebles en la Utilidad de los Estados Financieros: Una Nota de Investigación

    Directory of Open Access Journals (Sweden)

    Andrés Navarro Galera

    2009-06-01

    Full Text Available La elección en la reciente reforma contable española del criterio de valor razonable en lugar del coste histórico como base de valoración para determinados activos ha generado cierta controversia. Este trabajo estudia la posible incidencia de la adopción del valor razonable para el registro contable de los bienes inmuebles sobre la relevancia y la fiabilidad de la información financiera. El estudio empírico está basado en una encuesta sobre las percepciones de 151 responsables de la contabilidad de empresas españolas del sector de la construcción sobre la utilidad y fiabilidad de la información financiera basada en el valor razonable. El análisis de los resultados nos ha permitido concluir que, respecto al coste histórico, los responsables de contabilidad perciben que el valor razonable de los bienes inmuebles generaría estados financieros más útiles para representar la imagen fiel del patrimonio de la empresa. No obstante, los encuestados conciben la información financiera bajo valor razonable como menos objetiva y verificable. Asimismo, hemos comprobado que el tamaño de la empresa puede influir en la opinión de la repercusión del valor razonable sobre la relevancia y fiabilidad de los estados financieros.The option in the recent Spanish regulation for fair value over historical cost, as the preferred measurement basis for some assets, has raised some controversy. This paper studies the effects on accounting information relevance and reliability of fair value accounting for investment properties. The empirical study is based on a questionnairebased survey of the perceptions of 151 Spanish accountants in the building industry about the usefulness and reliability of fair value accounting. The analysis of results allows us concluding that accountants perceive that the usefulness of financial statements increases when investment property is valued on a fair value basis, compared with a historical cost basis. However, respondents

  19. Colloidal Quantum dot photovoltaics: Tuning optoelectronic properties

    International Nuclear Information System (INIS)

    Full text: Colloidal quantum dots combine processing from the solution phase with tunability of the bandgap. Via the size-effect the optical properties can be matched to the solar spectrum for a wide-range photon harvesting. To engineer photovoltaic devices, quantum dots are compressed from their colloidal form into a close-packed nanocrystal matrix, while undergoing a systematic layer-by-layer process. The resulting quantum dot solid is treated as semiconductor medium - one having electron-hole mobilites, free carrier densities and a dielectric constant. While the size-effect determined the band-gap before, it is now the nature of ligand and the treatment route, that influences mentioned electronic parameters. We took the view on the processing steps and found a concept for analysing trap states, moblility and device performance in real quantum dot solids. Our findings emphasize the interplay of mobility and trap-distribution with routes that take special care on the nanocrystal surface and hence conserve optoelectronic qualities of quantum dots for efficient photovoltaic cells. (author)

  20. Photoluminescence of carbon dots from mesoporous silica

    Science.gov (United States)

    Nelson, D. K.; Razbirin, B. S.; Starukhin, A. N.; Eurov, D. A.; Kurdyukov, D. A.; Stovpiaga, E. Yu; Golubev, V. G.

    2016-09-01

    Photophysical properties of carbon dots were investigated under various excitation conditions and over a wide temperature region - from room to liquid helium temperatures. The carbon dots (CDs) were synthesized using mesoporous silica particles as a reactor and (3-aminopropyl)triethoxysilane (APTES) as a precursor. The photoluminescence spectra of CDs exhibit a strong dependence on the excitation wavelength and demonstrate a significant inhomogeneous broadening. Lowering sample temperature reveals the doublet structure of the spectra, which is associated with the vibronic structure of radiative transitions. The vibration energy ∼1200 cm-1 is close to the energy of Csbnd O stretching vibration. Long-lived phosphorescence of carbon dots with its decay time ∼0.2 s at T = 80 K was observed. The fluorescence and phosphorescence spectra are shown to be spectrally separated. The long-lived component of the emission was ascribed to optically forbidden triplet-singlet transitions. The value of the singlet-triplet splitting was found to be about 0.3 eV. Photo-induced polarization of the luminescence of carbon dots was revealed. The degree of the linear polarization is dependent on the wavelengths of both excitation and emitted light. The effect indicates a hidden anisotropy of optical dipole transitions in the dots and demonstrates the loss of the dipole orientation during the electron energy relaxation.

  1. Inorganic passivation and doping control in colloidal quantum dot photovoltaics

    KAUST Repository

    Hoogland, Sjoerd H.

    2012-01-01

    We discuss strategies to reduce midgap trap state densities in colloidal quantum dot films and requirements to control doping type and magnitude. We demonstrate that these improvements result in colloidal quantum dot solar cells with certified 7.0% efficiency.

  2. Nanosized Carbon Dots from Organic Matter and Biomass

    Institute of Scientific and Technical Information of China (English)

    LI Yuanyuan; CHEN Tong; MA Yulong

    2016-01-01

    Carbon nanoparticles (C-dots) were prepared by relfuxing the combustion soots of candles and corn stalk in nitric acid. The synthesized C-dots were characterized. The results showed a sharp increase in oxygen content and a sharp decrease in carbon content after oxidation. The C-dots had -OH and -CO2H groups introduced which made them hydrophilic. However, their difference was also obvious. The C-dots from candle soot had a 10-45 nm broad particle size distribution, and those from corn stalk soot had a 6-18 nm relatively small and narrow size distribution. The C-dots were mainly ofsp2 andsp3 carbon structure different from the C-dots of diamond-like structure from candle soot. Interestingly, two kinds of C-dots all exhibited unique photoluminescent properties. The obtained C-dots have potential applications in a broad range of areas.

  3. Origins and optimization of entanglement in plasmonically coupled quantum dots

    Science.gov (United States)

    Otten, Matthew; Larson, Jeffrey; Min, Misun; Wild, Stefan M.; Pelton, Matthew; Gray, Stephen K.

    2016-08-01

    A system of two or more quantum dots interacting with a dissipative plasmonic nanostructure is investigated in detail by using a cavity quantum electrodynamics approach with a model Hamiltonian. We focus on determining and understanding system configurations that generate multiple bipartite quantum entanglements between the occupation states of the quantum dots. These configurations include allowing for the quantum dots to be asymmetrically coupled to the plasmonic system. Analytical solution of a simplified limit for an arbitrary number of quantum dots and numerical simulations and optimization for the two- and three-dot cases are used to develop guidelines for maximizing the bipartite entanglements. For any number of quantum dots, we show that through simple starting states and parameter guidelines, one quantum dot can be made to share a strong amount of bipartite entanglement with all other quantum dots in the system, while entangling all other pairs to a lesser degree.

  4. Filtering algorithm for dotted interferences

    Energy Technology Data Exchange (ETDEWEB)

    Osterloh, K., E-mail: kurt.osterloh@bam.de [Federal Institute for Materials Research and Testing (BAM), Division VIII.3, Radiological Methods, Unter den Eichen 87, 12205 Berlin (Germany); Buecherl, T.; Lierse von Gostomski, Ch. [Technische Universitaet Muenchen, Lehrstuhl fuer Radiochemie, Walther-Meissner-Str. 3, 85748 Garching (Germany); Zscherpel, U.; Ewert, U. [Federal Institute for Materials Research and Testing (BAM), Division VIII.3, Radiological Methods, Unter den Eichen 87, 12205 Berlin (Germany); Bock, S. [Technische Universitaet Muenchen, Lehrstuhl fuer Radiochemie, Walther-Meissner-Str. 3, 85748 Garching (Germany)

    2011-09-21

    An algorithm has been developed to remove reliably dotted interferences impairing the perceptibility of objects within a radiographic image. This particularly is a major challenge encountered with neutron radiographs collected at the NECTAR facility, Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II): the resulting images are dominated by features resembling a snow flurry. These artefacts are caused by scattered neutrons, gamma radiation, cosmic radiation, etc. all hitting the detector CCD directly in spite of a sophisticated shielding. This makes such images rather useless for further direct evaluations. One approach to resolve this problem of these random effects would be to collect a vast number of single images, to combine them appropriately and to process them with common image filtering procedures. However, it has been shown that, e.g. median filtering, depending on the kernel size in the plane and/or the number of single shots to be combined, is either insufficient or tends to blur sharp lined structures. This inevitably makes a visually controlled processing image by image unavoidable. Particularly in tomographic studies, it would be by far too tedious to treat each single projection by this way. Alternatively, it would be not only more comfortable but also in many cases the only reasonable approach to filter a stack of images in a batch procedure to get rid of the disturbing interferences. The algorithm presented here meets all these requirements. It reliably frees the images from the snowy pattern described above without the loss of fine structures and without a general blurring of the image. It consists of an iterative, within a batch procedure parameter free filtering algorithm aiming to eliminate the often complex interfering artefacts while leaving the original information untouched as far as possible.

  5. Bien rédiger

    CERN Document Server

    Humbert, Jean-Louis

    1992-01-01

    Vous avez à rédiger un rapport, un résumé, une note de service ou un compte rendu de réunion. Vous avez un examen écrit à préparer... Ce guide, enrichi de nombreux exercices, vous donne toutes les règles pour : . Formuler votre pensée . Structurer votre texte . Construire vos phrases . Choisir le mot juste.

  6. Coherence and dephasing in self-assembled quantum dots

    DEFF Research Database (Denmark)

    Hvam, Jørn Märcher; Leosson, K.; Birkedal, Dan

    2003-01-01

    We measured dephasing times in InGaAl/As self-assembled quantum dots at low temperature using degenerate four-wave mixing. At 0K, the coherence time of the quantum dots is lifetime limited, whereas at finite temperatures pure dephasing by exciton-phonon interactions governs the quantum dot...... coherence. The inferred homogeneous line widths are significantly smaller than the line widths usually observed in the photoluminescence from single quantum dots indicating an additional inhomogeneours broadening mechanism in the latter....

  7. Short-wave infrared colloidal quantum dot photodetectors on silicon

    OpenAIRE

    Hu, Chen; Gassenq, Alban; Justo, Yolanda; Yakunin, Sergii; Heiss, Wolfgang; Hens, Zeger; Roelkens, Gunther

    2013-01-01

    In this paper, two kinds of colloidal quantum dots, PbS and HgTe, are explored for SWIR photodetectors application. The colloidal dots are prepared by hot injection chemical synthesis, with organic ligands around the dots keeping them stable in solution. For the purpose of achieving efficient carrier transport between the dots in a film, these long organic ligands are replaced by shorter, inorganic ligands. We report uniform, ultra-smooth colloidal QD films without cracks realized by dip-coat...

  8. Quantum Dots in Photonic Crystal Waveguides

    DEFF Research Database (Denmark)

    Sollner, Immo Nathanael

    This Thesis is focused on the study of quantum electrodynamics in photonic crystal waveguides. We investigate the interplay between a single quantum dot and the fundamental mode of the photonic crystal waveguide. We demonstrate experimental coupling eciencies for the spontaneous emission...... into the mode exceeding 98% for emitters spectrally close to the band-edge of the waveguide mode. In addition we illustrate the broadband nature of the underlying eects, by obtaining coupling eciencies above 90% for quantum dots detuned from the band edge by as far as 20nm. These values are in good agreement...... quantum-dot-waveguide coupling. Such a structure is ideally suited for a number of applications in quantum information processing and among others we propose an on-chip spin-photon interface, a single photon transistor, and a deterministic cNOT gate....

  9. Charged-Exciton Complexes in Quantum Dots

    Institute of Scientific and Technical Information of China (English)

    XIE Wen-Fang

    2001-01-01

    It is known experimentally that stable charged-exciton complexes can exist in low-dimensional semiconductor nanostructures. Much less is known about the properties of such charged-exciton complexes since three-body problems are very difficult to be solved, even numerically. Here we introduce the correlated hyperspherical harmonics as basis functions to solve the hyperangular equation for negatively and positively charged excitons (trions) in a harmonic quantum dot. By using this method, we have calculated the energy spectra of the low-lying states of a charged exciton as a function of the radius of quantum dot. Based on symmetry analysis, the level crossover as the dot radius increases can be fully explained as the results of symmetry constraint.``

  10. Barrier Li Quantum Dots in Magnetic Fields

    Institute of Scientific and Technical Information of China (English)

    LIUYi-Min; LIXiao-Zhu; YANWen-Hong; BAOCheng-Guang

    2003-01-01

    The methods for the few-body system are introduced to investigate the states of the barrier Li quantum dots (QDs) in an arbitrary strength of magnetic field. The configuration, which consists of a positive ion located on the z-axis at a distaneed from the two-dimensional QD plane (the x-y plane) and three electrons in the dot plane bound by the positive ion, is called a barrier Li center. The system, which consists of three electrons in the dot plane bound by the ion,is called a barrier Li QD. The dependence of energy of the state of the barrier Li QD on an external magnetic field B and the distance d is obtained. The angular momentum L of the ground states is found to jump not only with the variation orB but also with d.

  11. Branch management into micropipeline joint dot

    Directory of Open Access Journals (Sweden)

    Dimitar Tyanev

    2011-11-01

    Full Text Available This paper considers problems related to hardware implementation of computational process with conditional jumps. Hardware refers to asynchronous pipeline organization at microoperational level. Exploration is dedicated to one of the tasks presented in (Tyanev, D., 2009 concerning to micropipeline controller design to control micropipeline stage into joint dot of branch algorithm. Joint dot is the point at which few preceding branches are combined. It appears inevitably into conditional jump structures and this is the reason for the actuality of its problem. Analysis of this new task is presented and request arbitration functioning principles are formulated for the incoming to joint dot requests. The arbiter is responsible for the fair choice on which depends steady peformance of separate pipeline brances. Paper also describes pipeline controller synthesis and analysis of its operation in two variants: about 2-phase and 4-phase data transfer protocol. The synthesized asynchronous arbiter scheme is invariant to the type of pipeline protocol.

  12. Valoración económica de bienes públicos: estudio de caso del río Lerma, La Piedad, Michoacán

    Directory of Open Access Journals (Sweden)

    Faustino Gómez Sántiz

    2015-01-01

    Full Text Available el tramo del río Lerma, que atraviesa la zona metropoli-tana de La Piedad de Cabadas, Michoacán-Santa Ana Pacue-co, Guanajuato, tiene una longitud de 12.8 km. Actualmenteestá convertido en un canal de desechos, que ha incididoen la aparición de fuertes problemas de salud pública. Eneste estudio se utilizó el método de valoración contingentey el modelo logit para determinar el valor económico totalde este bien ambiental, y para analizar las variables de ladecisión sobre la disposición a pagar una contribución pararealizar mejoras, por parte de los beneficiarios de él. Dichovalor se estimó en más de 4 millones de pesos anuales, estoindica que de realizarse mejoras ambientales, la poblaciónse beneficiaría en la medida en que se lograra mitigar losefectos de la contaminación.

  13. Producción y consumo de bienes culturales: El caso de las artesanías urbanas de la Ciudad de Buenos Aires

    Directory of Open Access Journals (Sweden)

    Mónica B. Rotman

    2002-12-01

    Full Text Available Este artículo tiene por objeto reseñar algunos de los principales aspectos de un fenómeno cultural citadino: las artesanías urbanas feriales de la Ciudad de Buenos Aires. La problemática abordada contempla las instancias de la producción artesanal, la circulación de estos bienes con énfasis en las Ferias como sitios privilegiados del intercambio y ámbitos relevantes de sociabilidad y el consumo de artesanías. Consideramos que este tipo de producción, que constituye un fenómeno complejo, conforma una práctica cultural heterodoxa, recreando con códigos propios la sociabilidad híbrida que inducen las ciudades contemporáneas.The objective of this article is to outline some of the main aspects of an urban cultural phenomenon: the urban handicrafts from fairs in Buenos Aires city. The issues this paper addresses are handicraft production, the circulation of these goods with emphasis on fairs as privileged places of exchange, sociability and handicraft consumption. I consider this type of production a complex phenomena that shapes an heterodox cultural practice, recreating through its own codes the hybrid sociability that contemporary cities induce.

  14. Aspectos generales del régimen de los bienes del litoral marítimo. Competencias y limitaciones sobre el Derecho de propiedad

    Directory of Open Access Journals (Sweden)

    Sebastián Barreto Cifuentes

    2013-06-01

    Full Text Available El concepto de “propiedad”, tradicionalmente estudiado con la lógica del Derecho privado, ha sufrido cambios internos (la función social como núcleo esencial y externos (las limitaciones administrativas que hacen necesario estudiarlo con herramientas lógicas y metodológicas del Derecho público. Se debe considerar que un derecho absoluto e ilimitado no requiere mayor atención por parte de la disciplina del Derecho público. La armonización y articulación de los derechos del propietario con las competencias asignadas a las autoridades administrativas, exige una particular atención para proteger los derechos ciudadanos. En desarrollo de lo mencionado, se ha realizado un corto estudio sobre los bienes del litoral marítimo, en particular de las competencias asignadas a las autoridades administrativas sobre estas áreas, así como el límite de estas competencias. También se presentará el análisis de algunos casos reales y potenciales en los cuales se hace necesaria la aplicación de garantías procesales y sustanciales para el respeto de los derechos de los propietarios.

  15. Hacia una reconstrucción del diseño legislativo del inventario y avalúo de los bienes hereditarios en Cuba

    Directory of Open Access Journals (Sweden)

    Raúl José Vega Cardona

    2014-12-01

    Full Text Available El presente artículo parte de la necesidad de realizar un estudio sobre el contenido del inventario y avalúo como operación particional del caudal hereditario en Cuba, a raíz de las complejidades propias del instituto, las que no solo se manifiestan en el ámbito teórico doctrinal sino también en la configuración legal que del mismo hiciera el legislador cubano. En este sentido se aporta, a partir de una exposición doctrinal sobre el tema, un diagnóstico de las principales insuficiencias que en el ámbito sustantivo inciden en la deficitaria práctica de la determinación y valuación de los bienes hereditarios, y con ello el establecimiento de las posibles pautas que permitan perfeccionar el régimen jurídico de la institución objeto de análisis.

  16. Aspectos generales del régimen de los bienes del litoral marítimo. Competencias y limitaciones sobre el Derecho de propiedad

    Directory of Open Access Journals (Sweden)

    Sebastián Barreto Cifuentes

    2013-07-01

    Full Text Available El concepto de “propiedad”, tradicionalmente estudiado con la lógica del Derecho privado, ha sufrido cambios internos (la función social como núcleo esencial y externos (las limitaciones administrativas que hacen necesario estudiarlo con herramientas lógicas y metodológicas del Derecho público. Se debe considerar que un derecho absoluto e ilimitado no requiere mayor atención por parte de la disciplina del Derecho público. La armonización y articulación de los derechos del propietario con las competencias asignadas a las autoridades administrativas, exige una particular atención para proteger los derechos ciudadanos. En desarrollo de lo mencionado, se ha realizado un corto estudio sobre los bienes del litoral marítimo, en particular de las competencias asignadas a las autoridades administrativas sobre estas áreas, así como el límite de estas competencias. También se presentará el análisis de algunos casos reales y potenciales en los cuales se hace necesaria la aplicación de garantías procesales y sustanciales para el respeto de los derechos de los propietarios.

  17. Optical properties of charged semiconductor quantum dots

    Science.gov (United States)

    Jha, Praket P.

    The effect of n-type doping on the luminescence properties of II-VI quantum dots is studied. The addition of two shells of CdS on CdSe quantum dots prevents the creation of surface traps and makes the system stable under reducing environment. The injection of electrons into films of quantum dots leads to lower photoluminescence (PL) efficiency, with the extent of quenching dependent on both the number and the quantum states of the spectator charges in the nanocrystal. It is found that a 1Pe electron is an eightfold better PL quencher than the 1Se electron. Reduced threshold for stimulated emission is also observed in doped CdSe/CdS films. Time resolved photoluminescence measurements are used to extract the recombination rates of a charged exciton, called trion. It is observed that the negative trion has a radiative rate ˜2.2 +/- 0.4x faster than a neutral exciton, while its non-radiative recombination rate is slower than the biexciton non-radiative recombination rate by a factor of 7.5 +/- 1.7. The knowledge of the recombination rates of the trion enables us to calculate the quantum yield of a negative trion to be ˜10% for the nanocrystals investigated in our work. This is larger than the off state quantum yield from a single quantum dot photoluminescence trajectory and eliminates the formation of negative trion as the possible reason for the PL blinking of single quantum dots. Single quantum dot electrochemistry has also been achieved. It is shown that by varying the Fermi level of the system electrons can be reversibly injected into and extracted out of single CdSe/CdS and CdSe/ZnS nanoparticles to modulate the photoluminescence.

  18. Bienes básicos, mercancía patrón y tasa de ganancia en Piero Sraffa Basic goods, standard commodity and the rate of profit in Piero Sraffa

    Directory of Open Access Journals (Sweden)

    Supelano Sarmiento Alberto

    1996-06-01

    Full Text Available Este ensayo describe el papel de los bienes básicos y la mercancía patrón en el esquema de precios de producción propuesto por Piero Sraffa. Su tema central son los problemas relacionados con la interpretación de Homero Cuevas: la importancia de los bienes básicos y de los bienes de lujo en la determinación de los precios y la distribución del excedente; la composición y el papel de la mercancía patrón; las limitaciones de la distinción entre los dos tipos de bienes y del concepto de mercancía patrón y la supuesta imposibilidad de construir la mercancía patrón.This essay describes the role of basic goods and the standard commodity in the prices of production scheme proposed by Piero Sraffa. Its central theme concerns the problems related to the interpretation of Homero Cuevas: the importance of basic goods and luxury goods in the determination of prices and the distribution of the surplus; the composition and role of the standard commodity; the limitations of the distinction between the two types of goods and theconcept of standard commodity and the supposed impossibility of constructing the standard commodity.

  19. Photoluminescence studies of single InGaAs quantum dots

    DEFF Research Database (Denmark)

    Leosson, Kristjan; Jensen, Jacob Riis; Hvam, Jørn Märcher

    1999-01-01

    Semiconductor quantum dots are considered a promising material system for future optical devices and quantum computers. We have studied the low-temperature photoluminescence properties of single InGaAs quantum dots embedded in GaAs. The high spatial resolution required for resolving single dots...

  20. Imaging vasculature and lymphatic flow in mice using quantum dots

    DEFF Research Database (Denmark)

    Ballou, Byron; Ernst, Lauren A.; Andreko, Susan;

    2009-01-01

    Quantum dots are ideal probes for fluorescent imaging of vascular and lymphatic tissues. On injection into appropriate sites, red- and near-infrared-emitting quantum dots provide excellent definition of vasculature, lymphoid organs, and lymph nodes draining both normal tissues and tumors. We detail...... methods for use with commercially available quantum dots and discuss common difficulties....

  1. AHE measurements of very thin films and nanosized dots

    NARCIS (Netherlands)

    Kikuchi, N.; Murillo, R.; Lodder, J.C.

    2005-01-01

    In this paper we present anomalous Hall effect analysis from very thin Co (0.5 nm) film, Co/Pt multilayers and large areas of nanosized dots as well as from a few magnetic dots having a diameter of 120 nm. The dot arrayis prepared from Co/Pt multilayer by using laser interference lithography (LIL) w

  2. Bright infrared LEDs based on colloidal quantum-dots

    KAUST Repository

    Sun, Liangfeng

    2013-01-01

    Record-brightness infrared LEDs based on colloidal quantum-dots have been achieved through control of the spacing between adjacent quantum-dots. By tuning the size of quantum-dots, the emission wavelengths can be tuned between 900nm and 1650nm. © 2013 Materials Research Society.

  3. Engineered Quantum Dot Single Photon Sources

    CERN Document Server

    Buckley, Sonia; Vuckovic, Jelena

    2012-01-01

    Fast, high efficiency, and low error single photon sources are required for implementation of a number of quantum information processing applications. The fastest triggered single photon sources to date have been demonstrated using epitaxially grown semiconductor quantum dots (QDs), which can be conveniently integrated with optical microcavities. Recent advances in QD technology, including demonstrations of high temperature and telecommunications wavelength single photon emission, have made QD single photon sources more practical. Here we discuss the applications of single photon sources and their various requirements, before reviewing the progress made on a quantum dot platform in meeting these requirements.

  4. Optical studies of capped quantum dots

    OpenAIRE

    Wuister, S.F.

    2005-01-01

    This thesis describes the synthesis and spectroscopy of CdSe and CdTe semiconductor quantum dots (QDs). The first chapter gives an introduction into the unique size dependent properties of semiconductor quantum dots. Highly luminescent QDs of CdSe and CdTe were prepared via a high temperature method in a glovebox. These QDs are soluble in organics but can be transferred into water or ethanol after exchange of the surfactants by various thiols (HS-R). For CdTe the exchange with thiols has a be...

  5. Cadmium telluride quantum dots advances and applications

    CERN Document Server

    Donegan, John

    2013-01-01

    Optical Properties of Bulk and Nanocrystalline Cadmium Telluride, Núñez Fernández and M.I. VasilevskiyAqueous Synthesis of Colloidal CdTe Nanocrystals, V. Lesnyak, N. Gaponik, and A. EychmüllerAssemblies of Thiol-Capped CdTe Nanocrystals, N. GaponikFörster Resonant Energy Transfer in CdTe Nanocrystal Quantum Dot Structures, M. Lunz and A.L. BradleyEmission of CdTe Nanocrystals Coupled to Microcavities, Y.P. Rakovich and J.F. DoneganBiological Applications of Cadmium Telluride Semiconductor Quantum Dots, A. Le Cign

  6. Resonant tunneling in graphene pseudomagnetic quantum dots.

    Science.gov (United States)

    Qi, Zenan; Bahamon, D A; Pereira, Vitor M; Park, Harold S; Campbell, D K; Neto, A H Castro

    2013-06-12

    Realistic relaxed configurations of triaxially strained graphene quantum dots are obtained from unbiased atomistic mechanical simulations. The local electronic structure and quantum transport characteristics of y-junctions based on such dots are studied, revealing that the quasi-uniform pseudomagnetic field induced by strain restricts transport to Landau level- and edge state-assisted resonant tunneling. Valley degeneracy is broken in the presence of an external field, allowing the selective filtering of the valley and chirality of the states assisting in the resonant tunneling. Asymmetric strain conditions can be explored to select the exit channel of the y-junction.

  7. Mitigation of quantum dot cytotoxicity by microencapsulation.

    Directory of Open Access Journals (Sweden)

    Amelia Romoser

    Full Text Available When CdSe/ZnS-polyethyleneimine (PEI quantum dots (QDs are microencapsulated in polymeric microcapsules, human fibroblasts are protected from acute cytotoxic effects. Differences in cellular morphology, uptake, and viability were assessed after treatment with either microencapsulated or unencapsulated dots. Specifically, QDs contained in microcapsules terminated with polyethylene glycol (PEG mitigate contact with and uptake by cells, thus providing a tool to retain particle luminescence for applications such as extracellular sensing and imaging. The microcapsule serves as the "first line of defense" for containing the QDs. This enables the individual QD coating to be designed primarily to enhance the function of the biosensor.

  8. A study of the lunisolar secular resonance $2dot{omega}+dot{Omega}=0$

    Directory of Open Access Journals (Sweden)

    Alessandra eCelletti

    2016-03-01

    Full Text Available The dynamics of small bodies around the Earth has gained a renewed interest,since the awareness of the problems that space debris can cause in thenearby future. A relevant role in space debris is played by lunisolarsecular resonances, which might contribute to an increase of the orbitalelements, typically of the eccentricity. We concentrate our attention onthe lunisolar secular resonance described by the relation$2dot{omega}+dot{Omega}=0$, where $omega$ and $Omega$ denotethe argument of perigee and the longitude of the ascending node of the space debris.We introduce three different models with increasing complexity. We show that the growth in eccentricity, as observed in space debris located in the MEO region at the inclination about equal to $56^circ$, can be explained as a natural effect of the secular resonance $2dot{omega}+dot{Omega}=0$, while the chaotic variations of the orbital parameters are the result of interaction and overlapping of nearby resonances.

  9. A study of the lunisolar secular resonance 2dot{ω}+dot{Ω}=0

    Science.gov (United States)

    Celletti, Alessandra; Gales, Catalin

    2016-03-01

    The dynamics of small bodies around the Earth has gained a renewed interest, since the awareness of the problems that space debris can cause in the nearby future. A relevant role in space debris is played by lunisolar secular resonances, which might contribute to an increase of the orbital elements, typically of the eccentricity. We concentrate our attention on the lunisolar secular resonance described by the relation 2dot{ω}+dot{Ω}=0, where ω and Ω denote the argument of perigee and the longitude of the ascending node of the space debris. We introduce three different models with increasing complexity. We show that the growth in eccentricity, as observed in space debris located in the MEO region at the inclination about equal to 56°, can be explained as a natural effect of the secular resonance 2dot{ω}+dot{Ω}=0, while the chaotic variations of the orbital parameters are the result of interaction and overlapping of nearby resonances.

  10. A study of the lunisolar secular resonance $2\\dot{\\omega}+\\dot{\\Omega}=0$

    CERN Document Server

    Celletti, Alessandra

    2016-01-01

    The dynamics of small bodies around the Earth has gained a renewed interest, since the awareness of the problems that space debris can cause in the nearby future. A relevant role in space debris is played by lunisolar secular resonances, which might contribute to an increase of the orbital elements, typically of the eccentricity. We concentrate our attention on the lunisolar secular resonance described by the relation $2\\dot{\\omega}+\\dot{\\Omega}=0$, where $\\omega$ and $\\Omega$ denote the argument of perigee and the longitude of the ascending node of the space debris. We introduce three different models with increasing complexity. We show that the growth in eccentricity, as observed in space debris located in the MEO region at the inclination about equal to $56^\\circ$, can be explained as a natural effect of the secular resonance $2\\dot{\\omega}+\\dot{\\Omega}=0$, while the chaotic variations of the orbital parameters are the result of interaction and overlapping of nearby resonances.

  11. Electrically addressing a single self-assembled quantum dot

    CERN Document Server

    Ellis, D J P; Atkinson, P; Ritchie, D A; Shields, A J

    2006-01-01

    We report on the use of an aperture in an aluminum oxide layer to restrict current injection into a single self-assembled InAs quantum dot, from an ensemble of such dots within a large mesa. The insulating aperture is formed through the wet-oxidation of a layer of AlAs. Under photoluminescence we observe that only one quantum dot in the ensemble exhibits a Stark shift, and that the same single dot is visible under electroluminescence. Autocorrelation measurements performed on the electroluminescence confirm that we are observing emission from a single quantum dot.

  12. The Influence of Formulating a Damping Solution on Dot Gain

    Directory of Open Access Journals (Sweden)

    Povilas Mikalainis

    2011-02-01

    Full Text Available Difference in dot gain using various additives to the damping solution was investigated on two offset web presses. Dot gain was measured using a densitometer and calculated considering CIE L*a*b* coordinates. It was found that while using a non alcohol additive instead of the alcohol one, dot gain became smaller and printing stability was lower. Changes in dot gain depend on the ink that may vary in colours. The influence of changes in dot gain on the colour was determined. Besides, it was found that differences in colour were unacceptable in many cases.Article in Lithuanian

  13. Synthesis of CdSe quantum dots for quantum dot sensitized solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Neetu, E-mail: singh.neetu1985@gmail.com; Kapoor, Avinashi [Department of Electronic Science, University of Delhi South Campus, New Delhi-110 021 (India); Kumar, Vinod [Department of Physics, University of the Free State, Bloemfontein, ZA9300 (South Africa); Mehra, R. M. [School of Engineering and Technology, Sharda University, Greater Noida-201 306, U.P. (India)

    2014-04-24

    CdSe Quantum Dots (QDs) of size 0.85 nm were synthesized using chemical route. ZnO based Quantum Dot Sensitized Solar Cell (QDSSC) was fabricated using CdSe QDs as sensitizer. The Pre-synthesized QDs were found to be successfully adsorbed on front ZnO electrode and had potential to replace organic dyes in Dye Sensitized Solar Cells (DSSCs). The efficiency of QDSSC was obtained to be 2.06 % at AM 1.5.

  14. Synthesis of CdSe quantum dots for quantum dot sensitized solar cell

    International Nuclear Information System (INIS)

    CdSe Quantum Dots (QDs) of size 0.85 nm were synthesized using chemical route. ZnO based Quantum Dot Sensitized Solar Cell (QDSSC) was fabricated using CdSe QDs as sensitizer. The Pre-synthesized QDs were found to be successfully adsorbed on front ZnO electrode and had potential to replace organic dyes in Dye Sensitized Solar Cells (DSSCs). The efficiency of QDSSC was obtained to be 2.06 % at AM 1.5

  15. Ostwald's ripening of nanostructures with quantum dots

    CERN Document Server

    Vengrenovich, R D; Yarema, S V

    2001-01-01

    The scenario of quantum dots shaping during ripening three-dimensional islands obtained by heteroepitaxy in a Stranski-Krastanow mode, is offered. It is shown that throughout the growth of dislocations with their subsequent separation from the island bottom, the size distribution function becomes narrower with noticeable diminishing the dispersion. The possible reasons for signal attenuation of Ostwald's ripening islands are analyzed

  16. Ostwald's ripening of nanostructures with quantum dots

    International Nuclear Information System (INIS)

    The scenario of quantum dots shaping during ripening three-dimensional islands obtained by heteroepitaxy in a Stranski-Krastanow mode, is offered. It is shown that throughout the growth of dislocations with their subsequent separation from the island bottom, the size distribution function becomes narrower with noticeable diminishing the dispersion. The possible reasons for signal attenuation of Ostwald's ripening islands are analyzed

  17. Saturating optical resonances in quantum dots

    Science.gov (United States)

    Nair, Selvakumar V.; Rustagi, K. C.

    Optical bistability in quantum dots, recently proposed by Chemla and Miller, is studied in a two-resonance model. We show that for such classical electromagnetic resonances the applicability of a two-resonance model is far more restrictive than for those in atoms.

  18. Quantum dot devices for optical communications

    DEFF Research Database (Denmark)

    Mørk, Jesper

    2005-01-01

    Semiconductor quantum dots are often described as "artificial atoms": They are small nanometre-sized structures in which electrons only are allowed to exist at certain discrete levels due to size quantization, thus allowing the engineering of fundamental properties such as the coupling to light. ...

  19. Single Molecule Applications of Quantum Dots

    DEFF Research Database (Denmark)

    Rasmussen, Thomas Elmelund; Jauffred, Liselotte; Brewer, Jonathan R.;

    2013-01-01

    Fluorescent nanocrystals composed of semiconductor materials were first introduced for biological applications in the late 1990s. The focus of this review is to give a brief survey of biological applications of quantum dots (QDs) at the single QD sensitivity level. These are described as follows: 1...

  20. Optical anisotropy in vertically coupled quantum dots

    DEFF Research Database (Denmark)

    Yu, Ping; Langbein, Wolfgang Werner; Leosson, Kristjan;

    1999-01-01

    We have studied the polarization of surface and edge-emitted photoluminescence (PL) from structures with vertically coupled In0.5Ga0.5As/GaAs quantum dots (QD's) grown by molecular beam epitaxy. The PL polarization is found to be strongly dependent on the number of stacked layers. While single...

  1. Decoherence in Nearly-Isolated Quantum Dots

    DEFF Research Database (Denmark)

    Folk, J.; M. Marcus, C.; Harris jr, J.

    2000-01-01

    Decoherence in nearly-isolated GaAs quantum dots is investigated using the change in average Coulomb blockade peak height upon breaking time-reversal symmetry. The normalized change in average peak height approaches the predicted universal value of 1/4 at temperatures well below the single...

  2. Producing Quantum Dots by Spray Pyrolysis

    Science.gov (United States)

    Banger, Kulbinder; Jin, Michael H.; Hepp, Aloysius

    2006-01-01

    An improved process for making nanocrystallites, commonly denoted quantum dots (QDs), is based on spray pyrolysis. Unlike the process used heretofore, the improved process is amenable to mass production of either passivated or non-passivated QDs, with computer control to ensure near uniformity of size.

  3. System and method for making quantum dots

    KAUST Repository

    Bakr, Osman M.

    2015-05-28

    Embodiments of the present disclosure provide for methods of making quantum dots (QDs) (passivated or unpassivated) using a continuous flow process, systems for making QDs using a continuous flow process, and the like. In one or more embodiments, the QDs produced using embodiments of the present disclosure can be used in solar photovoltaic cells, bio-imaging, IR emitters, or LEDs.

  4. 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.

  5. Quantum Dot Devices for Optical Signal Processing

    DEFF Research Database (Denmark)

    Chen, Yaohui

    with other semiconductor materials. The understanding of such properties is important in order to improve the performance of existing devices and to trigger the development of new semiconductor devices for dierent optical signal processing functionalities in the future. We present a detailed quantum dot...

  6. Competing interactions in semiconductor quantum dots

    NARCIS (Netherlands)

    R. van den Berg; G.P. Brandino; O. El Araby; R.M. Konik; V. Gritsev; J.S. Caux

    2014-01-01

    We introduce an integrability-based method enabling the study of semiconductor quantum dot models incorporating both the full hyperfine interaction as well as a mean-field treatment of dipole-dipole interactions in the nuclear spin bath. By performing free-induction decay and spin-echo simulations w

  7. Enabling biomedical research with designer quantum dots

    NARCIS (Netherlands)

    Tomczak, N.; Janczewski, D.; Dorokhin, D.V.; Han, M-Y; Vancso, G.J.; Navarro, Melba; Planell, Josep A.

    2012-01-01

    Quantum Dots (QDs) are a new class of semiconductor nanoparticulate luminophores, which are actively researched for novel applications in biology and nanomedicine. In this review, the recent progress in the design and applications of QD labels for in vitro and in vivo imaging of cells is presented.

  8. Quantum dot waveguides: ultrafast dynamics and applications

    DEFF Research Database (Denmark)

    Chen, Yaohui; Mørk, Jesper

    2009-01-01

    In this paper we analyze, based on numerical simulations, the dynamics of semiconductor devices incorporating quantum dots (QDs). In particular we emphasize the unique ultrafast carrier dynamics occurring between discrete QD bound states, and its influence on QD semiconductor optical amplifiers...

  9. Tunneling Processes in Optically Excited Quantum Dots

    Institute of Scientific and Technical Information of China (English)

    LI Xiu-Ping; WEI Hua-Rong; XU Li-Ping; GONG Jian-Ping; YAN Wei-Xian

    2011-01-01

    The single-electron tunneling processes in optically excited coupled quantum dots can be divided into two parts: the electron and the hole parts, which are analytically obtained in the framework of the Keldysh formalism. The tunneling process is selective tunneling, which results in dark tunneling states. The tunneling currents are co-determined by the resonance energies and probability distributions of the particular quantum channels defined by the electron-hole complex resonant states.%The single-electron tunneling processes in optically excited coupled quantum dots can be divided into two parts:the electron and the hole parts,which are analytically obtained in the framework of the Keldysh formalism.The tunneling process is selective tunneling,which results in dark tunneling states.The tunneling currents are co-determined by the resonance energies and probability distributions of the particular quantum channels defined by the electron-hole complex resonant states.Probing the fine-energy structure of the exciton complexes[1-10] in an optically excited quantum dot is an important way of exploring new mechanisms in nanostructures.Single electron tunneling (SET) devices consisting of a central quantum dot (QD) and a tunneling coupled source and drain have become important optoelectronic nano-devices.[11,12

  10. Inter-dot strain field effect on the optoelectronic properties of realistic InP lateral quantum-dot molecules

    International Nuclear Information System (INIS)

    We report on numerical simulations of InP surface lateral quantum-dot molecules on In0.48Ga0.52 P buffer, using a model strictly derived by experimental results by extrapolation of the molecules shape from atomic force microscopy images. Our study has been inspired by the comparison of a photoluminescence spectrum of a high-density InP surface quantum dot sample with a numerical ensemble average given by a weighted sum of simulated single quantum-dot spectra. A lack of experimental optical response from the smaller dots of the sample is found to be due to strong inter-dot strain fields, which influence the optoelectronic properties of lateral quantum-dot molecules. Continuum electromechanical, k→·p→ bandstructure, and optical calculations are presented for two different molecules, the first composed of two dots of nearly identical dimensions (homonuclear), the second of two dots with rather different sizes (heteronuclear). We show that in the homonuclear molecule the hydrostatic strain raises a potential barrier for the electrons in the connection zone between the dots, while conversely the holes do not experience any barrier, which considerably increases the coupling. Results for the heteronuclear molecule show instead that its dots do not appear as two separate and distinguishable structures, but as a single large dot, and no optical emission is observed in the range of higher energies where the smaller dot is supposed to emit. We believe that in samples of such a high density the smaller dots result as practically incorporated into bigger molecular structures, an effect strongly enforced by the inter-dot strain fields, and consequently it is not possible to experimentally obtain a separate optical emission from the smaller dots

  11. Inter-dot strain field effect on the optoelectronic properties of realistic InP lateral quantum-dot molecules

    Energy Technology Data Exchange (ETDEWEB)

    Barettin, Daniele, E-mail: Daniele.Barettin@uniroma2.it; Auf der Maur, Matthias [Department of Electronic Engineering, University of Rome “Tor Vergata,” Via del Politecnico 1, 00133, Rome (Italy); De Angelis, Roberta; Prosposito, Paolo; Casalboni, Mauro [Department of Industrial Engineering, University of Rome Tor Vergata, Via del Politecnico 1 00133 Rome, Italy and INSTM, Unitá di ricerca dell' Universitá di Roma “Tor Vergata,” Via della Ricerca Scientifica 1, 00133, Rome (Italy); Pecchia, Alessandro [CNR-ISMN, via Salaria Km. 29.300, 00017 Monterotondo, Rome (Italy)

    2015-03-07

    We report on numerical simulations of InP surface lateral quantum-dot molecules on In{sub 0.48}Ga{sub 0.52 }P buffer, using a model strictly derived by experimental results by extrapolation of the molecules shape from atomic force microscopy images. Our study has been inspired by the comparison of a photoluminescence spectrum of a high-density InP surface quantum dot sample with a numerical ensemble average given by a weighted sum of simulated single quantum-dot spectra. A lack of experimental optical response from the smaller dots of the sample is found to be due to strong inter-dot strain fields, which influence the optoelectronic properties of lateral quantum-dot molecules. Continuum electromechanical, k{sup →}·p{sup →} bandstructure, and optical calculations are presented for two different molecules, the first composed of two dots of nearly identical dimensions (homonuclear), the second of two dots with rather different sizes (heteronuclear). We show that in the homonuclear molecule the hydrostatic strain raises a potential barrier for the electrons in the connection zone between the dots, while conversely the holes do not experience any barrier, which considerably increases the coupling. Results for the heteronuclear molecule show instead that its dots do not appear as two separate and distinguishable structures, but as a single large dot, and no optical emission is observed in the range of higher energies where the smaller dot is supposed to emit. We believe that in samples of such a high density the smaller dots result as practically incorporated into bigger molecular structures, an effect strongly enforced by the inter-dot strain fields, and consequently it is not possible to experimentally obtain a separate optical emission from the smaller dots.

  12. Los bienes de interés cultural de Gáldar (Canarias y el conjunto histórico “Plaza de Santiago” (1981-2006

    Directory of Open Access Journals (Sweden)

    Juan Sebastián López García

    2013-10-01

    Full Text Available En 1981, hace veinticinco años, la zona central de Gáldar fue declarada “Conjunto Histórico Artístico” con la denominación de Plaza de Santiago. Sin embargo no era el primer bien cultural que obtenía una distinción de este tipo, ya que Gáldar había sido pionera en 1949 con el yacimiento de El Agujero y La Guancha, primero de los de carácter arqueológico declarado en Canarias, al que seguiría en 1972 la Cueva Pintada. Hasta la década de los setenta prevalecieron los bienes arqueológicos, situación que se modificó en las dos últimas décadas del siglo XX después del reconocimiento de la Plaza de Santiago y su entorno. Junto con edificaciones religiosas también se incluyeron ejemplos de arquitectura doméstica, completándose con algunos yacimientos prehispánicos. Una particular circunstancia fue la declaración en 1993 del pago de Barranco Hondo de Abajo, lo que convertía a Gáldar en el primer municipio de Canarias que contaba con dos conjuntos históricos, siendo éste a la vez el primero de la comunidad autonóma con características rurales. De la relación de los declarados, si exceptuamos la mayoría de los de carácter arqueológico, buena parte son urbanos. Una característica es que se incluyen categorías variadas, incluyendo la existencia de una zona arqueológica junto a un conjunto histórico y varios monumentos (de arquitectura religiosa y doméstica. Este hecho es lógico si se tiene en cuenta la particularidad de Gáldar y su condición de núcleo histórico de superposición.Twenty five years ago, in 1981, the central zone of Galdar was declared an "Historic Artistic Site" with the name of Plaza de Santiago. But this was not the first cultural asset to obtain a distinction of this kind, as Galdar pioneered protection of this kind with the El Agujero and La Guancha site, the first archaeological site declared in the Canary Islands, followed by La Cueva Pintada, in 1972. Archaeological assets prevailed up

  13. Annealing-induced change in quantum dot chain formation mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Park, Tyler D.; Colton, John S.; Farrer, Jeffrey K. [Department of Physics and Astronomy, Brigham Young University, Provo UT 84602 (United States); Yang, Haeyeon [Department of Nanoscience and Nanoengineering, South Dakota School of Mines and Technology, Rapid City, SD 57701 (United States); Kim, Dong Jun [IPG Photonics Corporation, Oxford, MA 01540 (United States)

    2014-12-15

    Self-assembled InGaAs quantum dot chains were grown using a modified Stranski-Krastanov method in which the InGaAs layer is deposited under a low growth temperature and high arsenic overpressure, which suppresses the formation of dots until a later annealing process. The dots are capped with a 100 nm GaAs layer. Three samples, having three different annealing temperatures of 460°C, 480°C, and 500°C, were studied by transmission electron microscopy. Results indicate two distinct types of dot formation processes: dots in the 460°C and 480°C samples form from platelet precursors in a one-to-one ratio whereas the dots in the sample annealed at 500°C form through the strain-driven self-assembly process, and then grow larger via an additional Ostwald ripening process whereby dots grow into larger dots at the expense of smaller seed islands. There are consequently significant morphological differences between the two types of dots, which explain many of the previously-reported differences in optical properties. Moreover, we also report evidence of indium segregation within the dots, with little or no indium intermixing between the dots and the surrounding GaAs barrier.

  14. Annealing-induced change in quantum dot chain formation mechanism

    Science.gov (United States)

    Park, Tyler D.; Colton, John S.; Farrer, Jeffrey K.; Yang, Haeyeon; Kim, Dong Jun

    2014-12-01

    Self-assembled InGaAs quantum dot chains were grown using a modified Stranski-Krastanov method in which the InGaAs layer is deposited under a low growth temperature and high arsenic overpressure, which suppresses the formation of dots until a later annealing process. The dots are capped with a 100 nm GaAs layer. Three samples, having three different annealing temperatures of 460°C, 480°C, and 500°C, were studied by transmission electron microscopy. Results indicate two distinct types of dot formation processes: dots in the 460°C and 480°C samples form from platelet precursors in a one-to-one ratio whereas the dots in the sample annealed at 500°C form through the strain-driven self-assembly process, and then grow larger via an additional Ostwald ripening process whereby dots grow into larger dots at the expense of smaller seed islands. There are consequently significant morphological differences between the two types of dots, which explain many of the previously-reported differences in optical properties. Moreover, we also report evidence of indium segregation within the dots, with little or no indium intermixing between the dots and the surrounding GaAs barrier.

  15. Annealing-induced change in quantum dot chain formation mechanism

    Directory of Open Access Journals (Sweden)

    Tyler D. Park

    2014-12-01

    Full Text Available Self-assembled InGaAs quantum dot chains were grown using a modified Stranski-Krastanov method in which the InGaAs layer is deposited under a low growth temperature and high arsenic overpressure, which suppresses the formation of dots until a later annealing process. The dots are capped with a 100 nm GaAs layer. Three samples, having three different annealing temperatures of 460°C, 480°C, and 500°C, were studied by transmission electron microscopy. Results indicate two distinct types of dot formation processes: dots in the 460°C and 480°C samples form from platelet precursors in a one-to-one ratio whereas the dots in the sample annealed at 500°C form through the strain-driven self-assembly process, and then grow larger via an additional Ostwald ripening process whereby dots grow into larger dots at the expense of smaller seed islands. There are consequently significant morphological differences between the two types of dots, which explain many of the previously-reported differences in optical properties. Moreover, we also report evidence of indium segregation within the dots, with little or no indium intermixing between the dots and the surrounding GaAs barrier.

  16. La evolución de las exportaciones de bienes de China: una visión panarómica = Chinese goods exports development: An overview

    Directory of Open Access Journals (Sweden)

    Ana Salvador Chamorro

    2013-12-01

    Full Text Available El proceso de reforma económica que ha experimentado la economía de China es uno de los fenómenos de mayor relevancia en la evolución de la Economía Mundial en los últimos treinta años y, sin duda, seguirá siéndolo en el futuro. Dentro de este proceso, la apertura al exterior, que el gobierno chino inició en 1978, ha situado al país en un lugar de máxima relevancia dentro de los flujos comerciales y financieros internacionales. En este contexto, el objetivo de este trabajo es intentar realizar un análisis general de la evolución del comercio exterior de China en las últimas décadas, prestando especial atención a sus exportaciones de bienes y poniendo énfasis en los cambios experimentados durante los últimos años.The process of economic reform that has experienced the Chinese economy is one of the most important events in the evolution of the World Economy in the past 30 years, and will undoubtedly remain so in the future. Within this economic reform, the opening process that the Chinese Government began in 1978, has put the country in a place of utmost importance in the international trade and financial flows. In this context, this paper try to perform an analysis of the evolution of China's foreign trade in recent decades, with particular attention to its exports and emphasizing the changes in recent years

  17. Honor femenino y economía de bienes simbólicos en Maracaibo, Venezuela, a finales del siglo XIX (1880 – 1900

    Directory of Open Access Journals (Sweden)

    Luis Rincón Rubio

    2008-05-01

    Full Text Available Se presenta en este trabajo una aproximación antropológica a las representaciones culturales del honor femenino circulantes en la ciudad de Maracaibo, Venezuela, a finales del siglo XIX. La investigación realizada adopta un enfoque teórico-metodológico de corte estructuralista-constructivista, abordando el orden social como un sistema simbólico organizado según una lógica de la diferencia y partiendo de la premisa de que prácticas y representaciones están orientadas externamente por las estructuras objetivas de la sociedad, e internamente por esquemas de percepción, pensamiento y acción de origen social. Al tratarse de un trabajo de antropología histórica, los informantes fueron sustituidos por fuentes documentales ubicadas en diferentes archivos venezolanos. Se encuentra que las representaciones culturales del honor femenino en la sociedad en cuestión asociaban este concepto con la castidad sexual, reproduciendo esquemas culturales vigentes en la órbita del mundo occidental y proporcionando una lógica para el mantenimiento de relaciones desiguales de género y poder en la vida pública y privada de los marabinos. El capital social y el capital simbólico habrían sido componentes fundamentales del capital total de que se disponía entonces en la lucha cotidiana por la obtención de recursos y por el reconocimiento social, en una economía de bienes simbólicos que atribuía al parecer preferentemente a los hombres el trabajo oficial de conservación o incremento de dichas formas de capital.

  18. La evolución de las exportaciones de bienes de China: una visión panarómica = Chinese goods exports development: An overview

    Directory of Open Access Journals (Sweden)

    Ana Salvador Chamorro

    2014-07-01

    Full Text Available Resumen El proceso de reforma económica que ha experimentado la economía de China es uno de los fenómenos de mayor relevancia en la evolución de la Economía Mundial en los últimos treinta años y, sin duda, seguirá siéndolo en el futuro. Dentro de este proceso, la apertura al exterior, que el gobierno chino inició en 1978, ha situado al país en un lugar de máxima relevancia dentro de los flujos comerciales y financieros internacionales. En este contexto, el objetivo de este trabajo es intentar realizar un análisis general de la evolución del comercio exterior de China en las últimas décadas, prestando especial atención a sus exportaciones de bienes y poniendo énfasis en los cambios experimentados durante los últimos años. Abstract The process of economic reform that has experienced the Chinese economy is one of the most important events in the evolution of the World Economy in the past 30 years, and will undoubtedly remain so in the future. Within this economic reform, the opening process that the Chinese Government began in 1978, has put the country in a place of utmost importance in the international trade and financial flows. In this context, this paper try to perform an analysis of the evolution of China's foreign trade in recent decades, with particular attention to its exports and emphasizing the changes in recent years.

  19. Inhomogeneous charging and screening effects in semiconductor quantum dot arrays

    Energy Technology Data Exchange (ETDEWEB)

    Wetzler, R [Institut fuer Theoretische Physik, Technische Universitaet Berlin, Hardenbergstr. 36, 10623 Berlin (Germany); Kunert, R [Institut fuer Theoretische Physik, Technische Universitaet Berlin, Hardenbergstr. 36, 10623 Berlin (Germany); Wacker, A [Fysiska Institutionen, Lunds Universitet, Box 118, 22100 Lund (Sweden); Schoell, E [Institut fuer Theoretische Physik, Technische Universitaet Berlin, Hardenbergstr. 36, 10623 Berlin (Germany)

    2004-07-01

    The electronic properties of quantum dot (QD) arrays are strongly influenced by the Coulomb interaction of electrons within the dot as well as with those in neighbouring dots. In this paper, we investigate this behaviour taking into account screening by a free electron gas in the vicinity of the QDs. We find pronounced effects for standard capacitance[ndash]voltage (CV) measurements of QD structures embedded in a pn-diode. In particular, we show that the three-dimensional nature of the problem is crucial for devices with low dot-density, whereas the self-consistency between electron depletion in the bulk layer and dot occupation is important for high dot-densities. The Coulomb interaction between the dots induces a broadening of the peaks in the CV characteristic which is comparable with the effect of disordered QD arrays, where we considered realistic size and position fluctuations obtained by a kinetic Monte Carlo simulation.

  20. Quantum dot-sized organic fluorescent dots for long-term cell tracing

    Science.gov (United States)

    Li, Kai; Tang, Ben Zhong; Liu, Bin

    2014-03-01

    Fluorescence techniques have been extensively employed to develop non-invasive methodologies for tracking and understanding complex biological processes both in vitro and in vivo, which is of high importance in modern life science research. Among a variety of fluorescent probes, inorganic semiconductor quantum dots (QDs) have shown advantages in terms of better photostability, larger Stokes shift and more feasible surface functionalization. However, their intrinsic toxic heavy metal components and unstable fluorescence at low pH greatly impede the applications of QDs in in vivo studies. In this work, we developed novel fluorescent probes that can outperform currently available QD based probes in practice. Using conjugated oligomer with aggregation-induced emission characteristics as the fluorescent domain and biocompatible lipid-PEG derivatives as the encapsulation matrix, the obtained organic dots have shown higher brightness, better stability in biological medium and comparable size and photostability as compared to their counterparts of inorganic QDs. More importantly, unlike QD-based probes, the organic fluorescent dots do not blink, and also do not contain heavy metal ions that could be potentially toxic when applied for living biosubstrates. Upon surface functionalization with a cell-penetrating peptide, the organic dots greatly outperform inorganic quantum dots in both in vitro and in vivo long-term cell tracing studies, which will be beneficial to answer crucial questions in stem cell/immune cell therapies. Considering the customized fluorescent properties and surface functionalities of the organic dots, a series of biocompatible organic dots will be developed to serve as a promising platform for multifarious bioimaging tasks in future.

  1. L’apprentissage du bien-être animal chez de futures professionnels animaliers : des éthiques animals malmenées

    Directory of Open Access Journals (Sweden)

    Vidal Michel

    2015-01-01

    Full Text Available Les débats dont le bien-être animal est l’objet entre chercheurs, professionnels et associations en font une question socialement vive scientifico-éthique. Ils en interrogent l’éducabilité alors que cette notion est prise en compte dans les curricula de l’enseignement agricole. Envisageant son enseignement au travers d’une éducation à l’empathie interspécifique, nous questionnons les facteurs susceptibles de l’influencer. Nous nous fondons sur le discours de sept élèves en baccalauréat professionnel relevant de l’élevage d’animaux de production ou d’animaux de compagnie durant deux années de formation. Six élèves, quelle que soit leur filière de formation, souhaitent créer une relation affective sans nécessairement développer une attitude empathique durant la formation. Parmi les facteurs responsables, nous distinguons (1 un manque de confiance en soi de l’élève, (2 des motivations égocentrées primant sur des motivations zoocentrées, (3 la loyauté et les habitudes acquises à l’égard des pratiques parentales, (4 la conformation aux pratiques et idéologies dominantes du monde professionnel, (5 des facteurs associés aux situations d’enseignement (savoirs et pratiques de référence qui font autorité, valeurs de conformité primant sur des valeurs éthiques, dissociation de la dimension relationnelle et productive de l’élevage, jugements négatifs portés par l’enseignant et les élèves originaires du monde agricole. Ces facteurs généreraient des mécanismes de défense chez l’élève nuisibles au développement d’un raisonnement affectivo-éthique critique.

  2. Bright infrared quantum-dot light-emitting diodes through inter-dot spacing control

    KAUST Repository

    Sun, Liangfeng

    2012-05-06

    Infrared light-emitting diodes are currently fabricated from direct-gap semiconductors using epitaxy, which makes them expensive and difficult to integrate with other materials. Light-emitting diodes based on colloidal semiconductor quantum dots, on the other hand, can be solution-processed at low cost, and can be directly integrated with silicon. However, so far, exciton dissociation and recombination have not been well controlled in these devices, and this has limited their performance. Here, by tuning the distance between adjacent PbS quantum dots, we fabricate thin-film quantum-dot light-emitting diodes that operate at infrared wavelengths with radiances (6.4 W sr \\'1 m \\'2) eight times higher and external quantum efficiencies (2.0%) two times higher than the highest values previously reported. The distance between adjacent dots is tuned over a range of 1.3 nm by varying the lengths of the linker molecules from three to eight CH 2 groups, which allows us to achieve the optimum balance between charge injection and radiative exciton recombination. The electroluminescent powers of the best devices are comparable to those produced by commercial InGaAsP light-emitting diodes. By varying the size of the quantum dots, we can tune the emission wavelengths between 800 and 1,850 nm.© 2012 Macmillan Publishers Limited.

  3. Interference effects in a double quantum dot system with inter-dot Coulomb correlations

    International Nuclear Information System (INIS)

    Electron transport through a double quantum dot system is studied with the use of the Green function formalism based on the equation of motion method, and an interplay between interference and Coulomb blockade effects due to inter-dot correlations is discussed. A double structure with two Fano resonances (or antiresonances) is found in the conductance spectrum. Fano features are weakly influenced by the presence of Coulomb interaction but the conductance is strongly suppressed in the energy region with the Fermi level in the leads close to the aligned levels of both dots. This Coulomb blockade effect takes place when the coupling between the dots is of repulsive character. On the other hand, the conductance of an artificial molecule with attractive inter-dot coupling is only slightly modified in this energy region. As a sign of the coupling can be easily changed in a presence of an external magnetic field by changes of the magnetic flux there is the possibility to control variations of the conductance, which may be important from the application point of view

  4. Entangling distant quantum dots using classical interference

    Science.gov (United States)

    Busch, Jonathan; Kyoseva, Elica S.; Trupke, Michael; Beige, Almut

    2008-10-01

    We show that it is possible to employ reservoir engineering to turn two distant and relatively bad cavities into one good cavity with a tunable spontaneous decay rate. As a result, quantum computing schemes, which would otherwise require the shuttling of atomic qubits in and out of an optical resonator, can now be applied to distant quantum dots. To illustrate this we transform a recent proposal to entangle two qubits via the observation of macroscopic fluorescence signals [J. Metz , Phys. Rev. Lett. 97, 040503 (2006)] to the electron-spin states of two semiconductor quantum dots. Our scheme requires neither the coherent control of qubit-qubit interactions nor the detection of single photons. Moreover, the scheme is relatively robust against spin-bath couplings, parameter fluctuations, and the spontaneous emission of photons.

  5. Mesoscopic Cavity Quantum Electrodynamics with Quantum Dots

    CERN Document Server

    Childress, L I; Lukin, M D

    2003-01-01

    We describe an electrodynamic mechanism for coherent, quantum mechanical coupling between spacially separated quantum dots on a microchip. The technique is based on capacitive interactions between the electron charge and a superconducting transmission line resonator, and is closely related to atomic cavity quantum electrodynamics. We investigate several potential applications of this technique which have varying degrees of complexity. In particular, we demonstrate that this mechanism allows design and investigation of an on-chip double-dot microscopic maser. Moreover, the interaction may be extended to couple spatially separated electron spin states while only virtually populating fast-decaying superpositions of charge states. This represents an effective, controllable long-range interaction, which may facilitate implementation of quantum information processing with electron spin qubits and potentially allow coupling to other quantum systems such as atomic or superconducting qubits.

  6. Many electron effects in semiconductor quantum dots

    Indian Academy of Sciences (India)

    R K Pandey; Manoj K Harbola; V Ranjan; Vijay A Singh

    2003-01-01

    Semiconductor quantum dots (QDs) exhibit shell structures, very similar to atoms. Termed as ‘artificial atoms’ by some, they are much larger (1 100 nm) than real atoms. One can study a variety of manyelectron effects in them, which are otherwise difficult to observe in a real atom. We have treated these effects within the local density approximation (LDA) and the Harbola–Sahni (HS) scheme. HS is free of the selfinteraction error of the LDA. Our calculations have been performed in a three-dimensional quantum dot. We have carried out a study of the size and shape dependence of the level spacing. Scaling laws for the Hubbard ‘’ are established.

  7. Magnetoconductance fluctuations in open bismuth quantum dots

    Science.gov (United States)

    Hackens, B.; Minet, J. P.; Farhi, G.; Crahay, A.; Faniel, S.; Gustin, C.; Bayot, V.

    2002-03-01

    We investigate the low temperature (300 mK - 10 K) magnetoconductance of open circular bismuth quantum dots (diameter: 500 nm). The structures are fabricated using a combination of electron beam lithography, lift off and plasma etching techniques on bismuth thin films evaporated on heated SiO2 substrates. We observe reproducible magnetoconductance fluctuations (UCFs) up to 5T, qualitatively similar to conductance fluctuations evidenced in open quantum dots patterned in high mobility semiconductor heterostructures. In our samples, UCFs are superposed on a slowly varying negative magnetoconductance background. We also observe a sharp conductance maximum centered in B=0, which is reminescent of the spin-orbit induced anti-localisation phenomenon. The behavior of UCFs and of the conductance maximum is discussed as a function of the temperature, thickness and degree of cristallinity of the cavity.

  8. Barrier Li Quantum Dots in Magnetic Fields

    Institute of Scientific and Technical Information of China (English)

    LIU Yi-Min; LI Xiao-Zhu; YAN Wen-Hong; BAO Cheng-Guang

    2003-01-01

    The methods for the few-body system are introduced to investigate the states of the barrier Li quantumdots (QDs) in an arbitrary strength of magnetic field. The configuration, which consists of a positive ion located on thez-axis at a distance d from the two-dimensional QD plane (the x-y plane) and three electrons in the dot plane boundby the positive ion, is called a barrier Li center. The system, which consists of three electrons in the dot plane bound bythe ion, is called a barrier Li QD. The dependence of energy of the state of the barrier Li QD on an external magneticfield B and the distance d is obtained. The angular momentum L of the ground states is found to jump not only withthe variation of B but also with d.

  9. Protease-activated quantum dot probes

    Science.gov (United States)

    Chang, Emmanuel; Sun, Jiantang; Miller, Jordan S.; Yu, William W.; Colvin, Vicki L.; West, Jennifer L.; Drezek, Rebekah

    2006-04-01

    We demonstrate a novel quantum dot based probe with inherent signal amplification upon interaction with a targeted proteolytic enzyme. This probe may be useful for imaging in cancer detection and diagnosis. In this system, quantum dots (QDs) are bound to gold nanoparticles (AuNPs) via a proteolytically-degradable peptide sequence to non-radiatively suppress luminescence. A 71% reduction in luminescence was achieved with conjugation of AuNPs to QDs. Peptide cleavage results in release of AuNPs and restores radiative QD photoluminescence. Initial studies observed a 52% rise in luminescence over 47 hours of exposure to 0.2 mg/mL collagenase. These probes can be customized for targeted degradation simply by changing the sequence of the peptide linker.

  10. Facile labeling of lipoglycans with quantum dots

    International Nuclear Information System (INIS)

    Bacterial endotoxins or lipopolysaccharides (LPS) are among the most potent activators of the innate immune system, yet mechanisms of their action and in particular the role of glycans remain elusive. Efficient non-invasive labeling strategies are necessary for studying interactions of LPS glycans with biological systems. Here we report a new method for labeling LPS and other lipoglycans with luminescent quantum dots. The labeling is achieved by partitioning of hydrophobic quantum dots into the core of various LPS aggregates without disturbing the native LPS structure. The biofunctionality of the LPS-Qdot conjugates is demonstrated by the labeling of mouse monocytes. This simple method should find broad applicability in studies concerned with visualization of LPS biodistribution and identification of LPS binding agents.

  11. Efficient Luminescence from Perovskite Quantum Dot Solids

    KAUST Repository

    Kim, Younghoon

    2015-11-18

    © 2015 American Chemical Society. Nanocrystals of CsPbX3 perovskites are promising materials for light-emitting optoelectronics because of their colloidal stability, optically tunable bandgap, bright photoluminescence, and excellent photoluminescence quantum yield. Despite their promise, nanocrystal-only films of CsPbX3 perovskites have not yet been fabricated; instead, highly insulating polymers have been relied upon to compensate for nanocrystals\\' unstable surfaces. We develop solution chemistry that enables single-step casting of perovskite nanocrystal films and overcomes problems in both perovskite quantum dot purification and film fabrication. Centrifugally cast films retain bright photoluminescence and achieve dense and homogeneous morphologies. The new materials offer a platform for optoelectronic applications of perovskite quantum dot solids.

  12. Light emission from Si quantum dots

    Directory of Open Access Journals (Sweden)

    Philippe M. Fauchet

    2005-01-01

    Full Text Available Si quantum dots (QDs as small as ∼2 nm in diameter have been synthesized by a variety of techniques. Because of quantum confinement and the elimination of bulk or surface defects, these dots can emit light from the near infrared throughout the visible with quantum efficiencies in excess of 10%. The luminescence wavelength range has been extended to longer wavelengths by the addition of light-emitting rare earths such as erbium (Er. Light-emitting devices (LEDs have been fabricated and their performances are starting to approach those of direct band gap semiconductor or organic LEDs. A search for a Si QD-based laser is even under way. The state-of-the-art in the materials science, physics, and device development of luminescent Si QDs is reviewed and areas of future research are pointed out.

  13. Ratiometric Temperature Sensing with Semiconducting Polymer Dots

    OpenAIRE

    Ye, Fangmao; Wu, Changfeng; Jin, Yuhui; Chan, Yang-Hsiang; Zhang, Xuanjun; Chiu, Daniel T.

    2011-01-01

    This communication describes ultra-bright single-nanoparticle ratiometric temperature sensors based on semiconducting polymer dots (Pdots). We attached the temperature sensitive dye—Rhodamine B (RhB), whose emission intensity decreases with increasing temperature—within the matrix of Pdots. The as-prepared Pdot-RhB nanoparticle showed excellent temperature sensitivity and high brightness because it took advantage of the light harvesting and amplified energy transfer capability of Pdots. More ...

  14. The Silicon:Colloidal Quantum Dot Heterojunction

    KAUST Repository

    Masala, Silvia

    2015-10-13

    A heterojunction between crystalline silicon and colloidal quantum dots (CQDs) is realized. A special interface modification is developed to overcome an inherent energetic band mismatch between the two semiconductors, and realize the efficient collection of infrared photocarriers generated in the CQD film. This junction is used to produce a sensitive near infrared photodetector. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Adiabatic description of nonspherical quantum dot models

    Energy Technology Data Exchange (ETDEWEB)

    Gusev, A. A., E-mail: gooseff@jinr.ru; Chuluunbaatar, O.; Vinitsky, S. I. [Joint Institute for Nuclear Research (Russian Federation); Dvoyan, K. G.; Kazaryan, E. M.; Sarkisyan, H. A. [Russian-Armenian (Slavonic) University (Armenia); Derbov, V. L.; Klombotskaya, A. S.; Serov, V. V. [Saratov State University (Russian Federation)

    2012-10-15

    Within the effective mass approximation an adiabatic description of spheroidal and dumbbell quantum dot models in the regime of strong dimensional quantization is presented using the expansion of the wave function in appropriate sets of single-parameter basis functions. The comparison is given and the peculiarities are considered for spectral and optical characteristics of the models with axially symmetric confining potentials depending on their geometric size, making use of the complete sets of exact and adiabatic quantum numbers in appropriate analytic approximations.

  16. Shot noise of coupled semiconductor quantum dots

    OpenAIRE

    Kiesslich, G.; Wacker, A; Schoell, E.

    2003-01-01

    The low-frequency shot noise properties of two electrostatically coupled semiconductor quantum dot states which are connected to emitter/collector contacts are studied. A master equation approach is used to analyze the bias voltage dependence of the Fano factor as a measure of temporal correlations in tunneling current caused by Pauli's exclusion principle and the Coulomb interaction. In particular, the influence of the Coulomb interaction on the shot noise behavior is discussed in detail and...

  17. SPECTRAL PROPERTIES OF SHUNGITE QUANTUM DOTS

    OpenAIRE

    RAZBIRIN B.S.; ROZHKOVA N.N.; Sheka, E. F.; Nelson, D. K.; Starukhin, A. N.; Goryunov, A. S.

    2014-01-01

    A low-temperature study has been performed for aqueous shungite, carbon tetrachloride, and toluene dispersions. Spectral characteristics for graphene quantum dots (GQDs) of shungite, attributed to individual fragments of reduced graphene oxide (rGO), reveal a dual character of the dispersions emitting centers: individual GQDs are responsible for the spectra position while fractal structure of GQD colloids provides large broadening of the spectra due to structural inhomogeneity of the colloida...

  18. Semiconductor Quantum Dots for Biomedicial Applications

    OpenAIRE

    Lijia Shao; Feng Yan; Yanfang Gao

    2011-01-01

    Semiconductor quantum dots (QDs) are nanometre-scale crystals, which have unique photophysical properties, such as size-dependent optical properties, high fluorescence quantum yields, and excellent stability against photobleaching. These properties enable QDs as the promising optical labels for the biological applications, such as multiplexed analysis of immunocomplexes or DNA hybridization processes, cell sorting and tracing, in vivo imaging and diagnostics in biomedicine. Meanwhile, QDs can...

  19. Quantum dots: synthesis, bioapplications, and toxicity

    OpenAIRE

    Valizadeh, Alireza; Mikaeili, Haleh; Samiei, Mohammad; Farkhani, Samad Mussa; Zarghami, Nosratalah; Kouhi, Mohammad; Akbarzadeh, Abolfazl; Davaran, Soodabeh

    2012-01-01

    This review introduces quantum dots (QDs) and explores their properties, synthesis, applications, delivery systems in biology, and their toxicity. QDs are one of the first nanotechnologies to be integrated with the biological sciences and are widely anticipated to eventually find application in a number of commercial consumer and clinical products. They exhibit unique luminescence characteristics and electronic properties such as wide and continuous absorption spectra, narrow emission spectra...

  20. The pinning effect in quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Monisha, P. J., E-mail: pjmonisha@gmail.com [School of Physics, University of Hyderabad, Hyderabad-500046 (India); Mukhopadhyay, Soma [Department of Physics, D V R College of Engineering and Technology, Hyderabad-502285 (India)

    2014-04-24

    The pinning effect is studied in a Gaussian quantum dot using the improved Wigner-Brillouin perturbation theory (IWBPT) in the presence of electron-phonon interaction. The electron ground state plus one phonon state is degenerate with the electron in the first excited state. The electron-phonon interaction lifts the degeneracy and the first excited states get pinned to the ground state plus one phonon state as we increase the confinement frequency.

  1. Depleted Bulk Heterojunction Colloidal Quantum Dot Photovoltaics

    KAUST Repository

    Barkhouse, D. Aaron R.

    2011-05-26

    The first solution-processed depleted bulk heterojunction colloidal quantum dot solar cells are presented. The architecture allows for high absorption with full depletion, thereby breaking the photon absorption/carrier extraction compromise inherent in planar devices. A record power conversion of 5.5% under simulated AM 1.5 illumination conditions is reported. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. The quantum dot nanoconjugate tool box (Invited Paper)

    Science.gov (United States)

    Tomlinson, I. D.; Wright, D. W.; Giorgio, T. D.; Blakely, R. D.; Pennycook, S. J.; Hercules, D.; Bentzen, L.; Smith, R. A.; McBride, J.; Vergne, M. J.; Rosenthal, S.

    2005-04-01

    The surface coating of quantum dots has been characterised using Z-stem. Quantum dots have been pegylated to increase stability in aqueous solution. The fluorescence intensity of the quantum dots was modulated pegylation. PEG was coupled using different ratios of EDC, PEG and NHS. Optimum coupling conditions were found to occur when 2000 equivalents of PEG were reacted with 1 equivalent of dot in the presence of 1500 equivalents of NHS and EDC. Angiotensin II was also conjugated to quantum dots and these conjugates were shown to be biologically active. Quantum dots have also been surface functionalised with other peptides such as NGR with subsequent demonstration of cell surface binding and can be characterized by flow cytometry.

  3. Templated self-assembly of SiGe quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Dais, Christian

    2009-08-19

    This PhD thesis reports on the fabrication and characterization of exact aligned SiGe quantum dot structures. In general, SiGe quantum dots which nucleate via the Stranski-Krastanov growth mode exhibit broad size dispersion and nucleate randomly on the surface. However, to tap the full potential of SiGe quantum dots it is necessary to control the positioning and size of the dots on a nanometer length, e.g. for electronically addressing of individual dots. This can be realized by so-called templated self-assembly, which combines top-down lithography with bottom-up selfassembly. In this process the lithographically defined pits serve as pre-defined nucleation points for the epitaxially grown quantum dots. In this thesis, extreme ultraviolet interference lithography at a wavelength of e=13.4 nm is employed for prepatterning of the Si substrates. This technique allows the precise and fast fabrication of high-resolution templates with a high degree of reproducibility. The subsequent epitaxial deposition is either performed by molecular beam epitaxy or low-pressure chemical vapour deposition. It is shown that the dot nucleation on pre-patterned substrates depends strongly on the lithography parameters, e.g. size and periodicity of the pits, as well as on the epitaxy parameters, e.g. growth temperature or material coverage. The interrelations are carefully analyzed by means of scanning force microscopy, transmission electron microscopy and X-ray diffraction measurements. Provided that correct template and overgrowth parameters are chosen, perfectly aligned and uniform SiGe quantum dot arrays of different period, size as well as symmetry are created. In particular, the quantum dot arrays with the so far smallest period (35 nm) and smallest size dispersion are fabricated in this thesis. Furthermore, the strain fields of the underlying quantum dots allow the fabrication of vertically aligned quantum dot stacks. Combining lateral and vertical dot alignment results in three

  4. Mode Competition in Dual-Mode Quantum Dots Semiconductor Microlaser

    CERN Document Server

    Chusseau, Laurent; Viktorovitch, P; Letartre, Xavier

    2013-01-01

    This paper describes the modeling of quantum dots lasers with the aim of assessing the conditions for stable cw dual-mode operation when the mode separation lies in the THz range. Several possible models suited for InAs quantum dots in InP barriers are analytically evaluated, in particular quantum dots electrically coupled through a direct exchange of excitation by the wetting layer or quantum dots optically coupled through the homogeneous broadening of their optical gain. A stable dual-mode regime is shown possible in all cases when quantum dots are used as active layer whereas a gain medium of quantum well or bulk type inevitably leads to bistable behavior. The choice of a quantum dots gain medium perfectly matched the production of dual-mode lasers devoted to THz generation by photomixing.

  5. Modified magnetic quantum dot with electric confining potentials

    International Nuclear Information System (INIS)

    The electronic properties of a modified magnetic quantum dot are studied. The modified magnetic quantum dot is a quantum structure that is formed by spatially inhomogeneous distributions of magnetic fields. Electrons are magnetically confined to the plane where the magnetic fields inside and outside the dot are different from each other. The energy spectrum exhibits quite different features depending on the directions of the magnetic fields inside and outside the dot. In particular, the case of opposite directions of the fields is more interesting than that of the same direction. An electrostatic potential is introduced to the system to study the effects of an electric confining potential on the eigenenergy of a single electron in the modified magnetic quantum dot. The additional potential raises the whole energy spectrum and changes its shape. The ground-state angular momentum transitions occurring in a bare modified magnetic quantum dot disappear on introduction of the additional parabolic potential

  6. Ac response of a coupled double quantum dot

    Institute of Scientific and Technical Information of China (English)

    Xu Jie; W.Z. Shangguan; Zhan Shi-Chang

    2005-01-01

    The effect of phase-breaking process on the ac response of a coupled double quantum dot is studied in this paper based on the nonequilibrium Green function formalism. A general expression is derived for the ac current in the presence of electron-phonon interaction. The ac conductance is numerically computed and the results are compared with those in [Anatram M P and Datts S 1995 Phys. Rev. B 51 7632]. Our results reveal that the inter-dot electron tunnelling interplays with that between dots and electron reservoirs, and contributes prominently to the ac current when inter-dot tunnelling coupling is much larger than the tunnelling coupling between dots and electron reservoirs. In addition, the phase-breaking process is found to have a significant effect on the ac transport through the coupled double dot.

  7. Single quantum dots fundamentals, applications, and new concepts

    CERN Document Server

    2003-01-01

    This book reviews recent advances in the exciting and rapid growing field of semiconductor quantum dots by contributions from some of the most prominent researchers in the field. Special focus is given to the optical and electronic properties of single quantum dots due to their potential applications in devices operating with single electrons and/or single photons. This includes quantum dots in electric and magnetic fields, cavity-quantum electrodynamics, nonclassical light generation, and coherent optical control of excitons. Single Quantum Dots also addresses various growth techniques as well as potential device applications such as quantum dot lasers, and new concepts like a single-photon source, and a single quantum dot laser.

  8. Quantum Dots and Their Multimodal Applications: A Review

    Directory of Open Access Journals (Sweden)

    Paul H. Holloway

    2010-03-01

    Full Text Available Semiconducting quantum dots, whose particle sizes are in the nanometer range, have very unusual properties. The quantum dots have band gaps that depend in a complicated fashion upon a number of factors, described in the article. Processing-structure-properties-performance relationships are reviewed for compound semiconducting quantum dots. Various methods for synthesizing these quantum dots are discussed, as well as their resulting properties. Quantum states and confinement of their excitons may shift their optical absorption and emission energies. Such effects are important for tuning their luminescence stimulated by photons (photoluminescence or electric field (electroluminescence. In this article, decoupling of quantum effects on excitation and emission are described, along with the use of quantum dots as sensitizers in phosphors. In addition, we reviewed the multimodal applications of quantum dots, including in electroluminescence device, solar cell and biological imaging.

  9. Controlled coupling of quantum dots to nanowire plasmons

    International Nuclear Information System (INIS)

    Full text: The diameter of dielectric waveguides is limited by the wavelength of the guided light. In contrast, gold and silver nanowires can sustain propagating plasmon modes even for significantly smaller dimensions. Furthermore the strong eld localization of the nanowire plasmon modes leads to a strong interaction with nearby quantum emitters such as quantum dots. We use electron beam lithography, rst, to fabricate silver nanowires and, second, to position a few dots close to one nanowire end in a template-assisted process. Scanning a focused laser spot over the nanowire ends, we demonstrate both, the excitation of nanowire modes by quantum dots and the addressing of the same dots by plasmons. We use the fluorescence signals to quantify the quantum dots/plasmon coupling and show that part of the plasmon-induced dot fluorescence couples back to plasmonic modes. (author)

  10. Quantum dot spectroscopy using a single phosphorus donor

    Science.gov (United States)

    Büch, Holger; Fuechsle, Martin; Baker, William; House, Matthew G.; Simmons, Michelle Y.

    2015-12-01

    Using a deterministic single P donor placed with atomic precision accuracy next to a nanoscale silicon quantum dot, we present a way to analyze the energy spectrum of small quantum dots in silicon by tunnel-coupled transport measurements. The energy-level structure of the quantum dot is observed as resonance features within the transport bias triangles when the donor chemical potential is aligned with states within the quantum dot as confirmed by a numeric rate equation solver SIMON. This technique allows us to independently extract the quantum dot level structure irrespective of the density of states in the leads. Such a method is useful for the investigation of silicon quantum dots in the few-electron regime where the level structure is governed by an intricate interplay between the spin- and the valley-orbit degrees of freedom.

  11. Luminescent GdVO4:Sm3+ quantum dots enhance power conversion efficiency of bulk heterojunction polymer solar cells by Förster resonance energy transfer

    Science.gov (United States)

    Bishnoi, Swati; Gupta, Vinay; Sharma, Chhavi; Haranath, D.; Naqvi, Sheerin; Kumar, Mahesh; Sharma, Gauri D.; Chand, Suresh

    2016-07-01

    In this work, we report enhanced power conversion efficiency (PCE) of bulk heterojunction polymer solar cells by Förster resonance energy transfer (FRET) from samarium-doped luminescent gadolinium orthovanadate (GdVO4:Sm3+) quantum dots (QDs) to polythieno[3,4-b]-thiophene-co-benzodithiophene (PTB7) polymer. The photoluminescence emission spectrum of GdVO4:Sm3+ QDs overlaps with the absorption spectrum of PTB7, leading to FRET from GdVO4:Sm3+ to PTB7, and significant enhancements in the charge-carrier density of excited and polaronic states of PTB7 are observed. This was confirmed by means of femtosecond transient absorption spectroscopy. The FRET from GdVO4:Sm3+ QDs to PTB7 led to a remarkable increase in the power conversion efficiency (PCE) of PTB7:GdVO4:Sm3+:PC71BM ([6,6]-phenyl-C71-butyric acid methyl ester) polymer solar cells. The PCE in optimized ternary blend PTB7:GdVO4:Sm3+:PC71BM (1:0.1:1.5) is increased to 8.8% from 7.2% in PTB7:PC71BM. This work demonstrates the potential of rare-earth based luminescent QDs in enhancing the PCE of polymer solar cells.

  12. Study of inter-dot coupling in nano-patterned permalloy dots array

    International Nuclear Information System (INIS)

    We present a series of studies on interdot coupling in the nanometer-scaled permalloy dots array. A standard electron beam lithography in conjunction with lift-off process was employed for patterning 30 nm thick of millions of permalloy dots array with diameter (D) of 500 nm and the aspect ratio S/D of spacing (S) to diameter ranging from 0.2 to 1.25. The magnetization reversal processes were identified to evolve through the vortex nucleation, movement, and annihilation based on magnetic force microscopy (MFM) imaging in the presence of external magnetic fields. The nucleation field, annihilation field, and moving rate of vortex core were analyzed using M-H loops measured by the alternating gradient magnetometer (AGM). These behaviors are associated with the dipole-dipole interaction in dots array with various interdot spacings.

  13. Electron States of Few-Electron Quantum Dots

    Institute of Scientific and Technical Information of China (English)

    戴振宏; 孙金祚; 张立德; 李作宏; 黄士勇; 隋鹏飞

    2002-01-01

    We study few-electron semiconductor quantum dots using the unrestricted Hartree-Fock-Roothaan method based on the Gaussian basis. Our emphasis is on the energy level calculation for quantum dots. The confinement potential in a quantum dot is assumed to be in a form of three-dimensional spherical finite potential well. Some valuable results, such as the rearrangement of the energy level, have been obtained.

  14. Exciton dephasing in single InGaAs quantum dots

    DEFF Research Database (Denmark)

    Leosson, Kristjan; Østergaard, John Erland; Jensen, Jacob Riis;

    2000-01-01

    The homogeneous linewidth of excitonic transitions is a parameter of fundamental physical importance. In self-assembled quantum dot systems, a strong inhomogeneous broadening due to dot size fluctuations masks the homogeneous linewidth associated with transitions between individual states. The ho...... to fast dephasing. We present an investigation of the low-temperature homogeneous linewidth of individual PL lines from MBE-grown In0.5Ga0.5As/GaAs quantum dots....

  15. Exciton lifetime measurements on single silicon quantum dots.

    Science.gov (United States)

    Sangghaleh, Fatemeh; Bruhn, Benjamin; Schmidt, Torsten; Linnros, Jan

    2013-06-01

    We measured the exciton lifetime of single silicon quantum dots, fabricated by electron beam lithography, reactive ion etching and oxidation. The observed photoluminescence decays are of mono-exponential character with a large variation (5-45 μs) from dot to dot, even for the same emission energy. We show that this lifetime variation may be the origin of the heavily debated non-exponential (stretched) decays typically observed for ensemble measurements.

  16. Region-Dot Conversion Fusion Algorithm and Application

    OpenAIRE

    Zhouxing Fu; Mei Wang; Jingyi Du; Hsiung-Cheng Lin; Ningbo Xu; Hongyang Zan

    2014-01-01

    The interior decoration materials and the new furniture using formaldehyde, ammonia, and other poisonous substances are known as the main sources of indoor air pollutions. However, it is still a big challenge to estimate accurately the overall air quality by using the current measuring tools. Accordingly, the region-dot fusion (RDF) algorithm is proposed to evaluate the air quality in this paper. For the conversion from a region to a dot, the region-dot function is firstly defined as the summ...

  17. Nonlinear transport in coupled quantum dots: A stationary probability approach

    Institute of Scientific and Technical Information of China (English)

    GONG JianPing; DUAN SuQing; YAN WeiXian; ZHAO XianGeng

    2009-01-01

    The stationary tunneling current and differential conductance of the coupled quantum dots system with split-gates are calculated by generalizing the Beenaker's linear response theory for the description of the Coulomb-blockade oscillations of the conductance in the single quantum dot. The calculation of the charging diagram in parallel through the double dot as function of the two side-gate voltages shows a remarkable agreement with the recent experimental results by Hatano et al. (Science, 2005, 309: 268-271)

  18. Recent advances in carbon-based dots for electroanalysis.

    Science.gov (United States)

    Yulong, Ying; Xinsheng, Peng

    2016-04-25

    Carbon-based dots represent a new type of quantum dot with unique and well-defined properties owing to their quantum confinement and edge effects, which are widely employed in sensing, light-emitting diodes, nanomedicine, photocatalysis, electrocatalysis, bioimaging, etc. In this review, we update the latest research results of carbon-based dots in this rapidly evolving field of electroanalysis, place emphases on their applications as sensors and give future perspectives for developing more smart sensors.

  19. Polarization anisotropic luminescence of tunable single lateral quantum dot molecules

    Science.gov (United States)

    Hermannstädter, C.; Witzany, M.; Heldmaier, M.; Hafenbrak, R.; Jöns, K. D.; Beirne, G. J.; Michler, P.

    2012-03-01

    We investigate the photoluminescence polarization anisotropy of self-assembled individual lateral InGaAs/GaAs quantum dot molecules. In contrast to similarly grown single quantum dots, the dot molecules exhibit a remarkable degree of linear polarization, which remains almost unchanged when a lateral electric field is applied to tune the exciton wave function and, thus, the luminescence spectral properties. We discuss the nature of this polarization anisotropy and suggest possible causes based on the system's symmetry and heterostructure alloy composition.

  20. Reconfigurable quadruple quantum dots in a silicon nanowire transistor

    OpenAIRE

    Betz, A. C.; Tagliaferri, M. L. V.; Vinet, M.; Broström, M.; Sanquer, M.; Ferguson, A.J.; Gonzalez-Zalba, M. F.

    2016-01-01

    We present a novel reconfigurable metal-oxide-semiconductor multi-gate transistor that can host a quadruple quantum dot in silicon. The device consist of an industrial quadruple-gate silicon nanowire field-effect transistor. Exploiting the corner effect, we study the versatility of the structure in the single quantum dot and the serial double quantum dot regimes and extract the relevant capacitance parameters. We address the fabrication variability of the quadruple-gate approach which, paired...

  1. Polarized quantum dot emission in electrohydrodynamic jet printed photonic crystals

    Energy Technology Data Exchange (ETDEWEB)

    See, Gloria G. [Micro and Nanotechnology Laboratory, Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, 208 North Wright Street, Urbana, Illinois 61801 (United States); Xu, Lu; Nuzzo, Ralph G. [Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801 (United States); Sutanto, Erick; Alleyne, Andrew G. [Mechanical Science and Engineering Department, University of Illinois at Urbana-Champaign, 154 Mechanical Engineering Building, Urbana, Illinois 61801 (United States); Cunningham, Brian T. [Micro and Nanotechnology Laboratory, Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, 208 North Wright Street, Urbana, Illinois 61801 (United States); Department of Bioengineering, University of Illinois at Urbana-Champaign, 1270 Digital Computer Laboratory, MC-278, Urbana, Illinois 61801 (United States)

    2015-08-03

    Tailored optical output, such as color purity and efficient optical intensity, are critical considerations for displays, particularly in mobile applications. To this end, we demonstrate a replica molded photonic crystal structure with embedded quantum dots. Electrohydrodynamic jet printing is used to control the position of the quantum dots within the device structure. This results in significantly less waste of the quantum dot material than application through drop-casting or spin coating. In addition, the targeted placement of the quantum dots minimizes any emission outside of the resonant enhancement field, which enables an 8× output enhancement and highly polarized emission from the photonic crystal structure.

  2. Nonequilibrium Electron Transport Through a Quantum Dot from Kubo Formula

    Institute of Scientific and Technical Information of China (English)

    L(U) Rong; ZHANG Guang-Ming

    2005-01-01

    Based on the Kubo formula for an electron tunneling junction, we revisit the nonequilibrium transport properties through a quantum dot. Since the Fermi level of the quantum dot is set by the conduction electrons of the leads, we calculate the electron current from the left side by assuming the quantum dot coupled to the right lead as another side of the tunneling junction, and the other way round is used to calculate the current from the right side. By symmetrizing these two currents, an effective local density states on the dot can be obtained, and is discussed at high and low temperatures, respectively.

  3. Coupling of single quantum dots to a photonic crystal waveguide

    DEFF Research Database (Denmark)

    Lund-Hansen, Toke; Stobbe, Søren; Julsgaard, Brian;

    is coupled efficiently to a single enhanced mode. One popular approach has been to couple single quantum dots to a nanocavity but a limiting factor in this configuration is that in order to apply the photon it should subsequently be coupled out of the cavity, reducing the overall efficiency significantly....... An alternative approach is to couple the quantum dot directly to the propagating mode of a photonic waveguide. We demonstrate the coupling of single quantum dots to a photonic crystal waveguide using time-resolved spontaneous emission measurements. A pronounced effect is seen in the decay rates of dots coupled...

  4. An Exciton Bound to a Neutral Donor in Quantum Dots

    Institute of Scientific and Technical Information of China (English)

    解文方

    2002-01-01

    The binding energies for an exciton (X) trapped in a two-dimensional quantum dot by a neutral donor have been calculated using the method of few-body physics for the heavy hole (σ= 0.196) and the light hole (σr = 0.707).We find that the (D0, X) complex confined in a quantum dot has in general a larger binding energy than those in a two-dimensional quantum well and a three-dimensional bulk semiconductor, and the binding energy increases with the decrease of the dot radius. At dot radius R →∞, we compare our calculated result with the previous results.

  5. Core–shell quantum dots: Properties and applications

    Energy Technology Data Exchange (ETDEWEB)

    Vasudevan, D., E-mail: vasudevand@rediffmail.com [Electrodics and electrocatalysis division, CSIR-CECRI, Karaikudi 630006 (India); Gaddam, Rohit Ranganathan [Amity Institute of Nanotechnology, Amity University, Noida 201301 (India); Trinchi, Adrian; Cole, Ivan [CSIRO Materials Science and Engineering, Clayton South MDC, 3169 (Australia)

    2015-07-05

    Fluorescent quantum dots (QDs) are semiconducting nanocrystals (NCs) that find numerous applications in areas, such as bio labelling, sensors, lasers, light emitting diodes and medicine. Core–shell quantum dots were developed to improve the photoluminescence efficiency of single quantum dots. Capping their surface with organic ligands as well as their extraction into aqueous media enables their use in sensing applications. The current review highlights the importance and applications of core shell quantum dots as well as their surface modifications and applications in the field of medicine and as sensors for chemical and biochemical analysis.

  6. Carbon Dot Based Sensing of Dopamine and Ascorbic Acid

    OpenAIRE

    Upama Baruah; Neelam Gogoi; Achyut Konwar; Manash Jyoti Deka; Devasish Chowdhury; Gitanjali Majumdar

    2014-01-01

    We demonstrate carbon dot based sensor of catecholamine, namely, dopamine and ascorbic acid. Carbon dots (CDs) were prepared from a green source: commercially available Assam tea. The carbon dots prepared from tea had particle sizes of ∼0.8 nm and are fluorescent. Fluorescence of the carbon dots was found to be quenched in the presence of dopamine and ascorbic acid with greater sensitivity for dopamine. The minimum detectable limits were determined to be 33 μM and 98 μM for dopamine and ascor...

  7. Highly fluorescent xerogels with entrapped carbon dots for organic scintillators

    Energy Technology Data Exchange (ETDEWEB)

    Quaranta, A., E-mail: quaranta@ing.unitn.it [University of Trento, Department of Industrial Engineering, via Mesiano, 77, 38123 Trento (Italy); Laboratori Nazionali di Legnaro, INFN, Viale dell' Università, 2, 35020 Legnaro (PD) (Italy); Carturan, S. [Laboratori Nazionali di Legnaro, INFN, Viale dell' Università, 2, 35020 Legnaro (PD) (Italy); University of Padova, Department of Physics and Astronomy “Galileo Galilei”, Via Marzolo, 8, 35131 Padova (Italy); Campagnaro, A.; Dalla Palma, M. [University of Trento, Department of Industrial Engineering, via Mesiano, 77, 38123 Trento (Italy); Laboratori Nazionali di Legnaro, INFN, Viale dell' Università, 2, 35020 Legnaro (PD) (Italy); Giarola, M.; Daldosso, N. [University of Verona, Department of Informatics, Strada le Grazie,15, 37134 Verona (Italy); Maggioni, G. [Laboratori Nazionali di Legnaro, INFN, Viale dell' Università, 2, 35020 Legnaro (PD) (Italy); University of Padova, Department of Physics and Astronomy “Galileo Galilei”, Via Marzolo, 8, 35131 Padova (Italy); Mariotto, G. [University of Verona, Department of Informatics, Strada le Grazie,15, 37134 Verona (Italy)

    2014-02-28

    Organically modified silicate thin film and bulk samples were prepared using [3-(2-aminoethylamino)propyl]trimethoxysilane (AEAP-TMOS) as precursor with the addition of different amounts of AEAP-TMOS functionalized C-dots, prepared by reaction of AEAP-TMOS and citric acid at high temperature. The synthesis of surface functionalized C-dots was followed by Fourier Transform Infrared (FTIR) spectroscopy, and the C-dots optical properties were characterized by optical absorption and UV–vis fluorescence. Thin xerogel films and bulk samples were studied by FTIR, Raman and fluorescence spectroscopy. Intense blue-green emission was observed by UV excitation of functionalized C-dots. Carbon quantum dot (CQD) luminescence was preserved also in the xerogel matrices, and the energy transfer from the matrix to CQDs, which is a key characteristic for scintillation detectors, was investigated in the two systems. - Highlights: • Functionalized carbon dots were synthesized. • Carbon dots were dispersed in hybrid xerogel bulk and thin film. • Carbon dots exhibit a strong tunable blue luminescence. • Xerogels were characterized by FT-IR, Raman and fluorescence spectroscopies. • Energy transfer processes were evidenced between C-dots and xerogel matrix.

  8. 我是中国DotA的希望(一)

    Institute of Scientific and Technical Information of China (English)

    少小帅

    2010-01-01

    我叫贾鹏我叫贾鹏,我是中国DotA的希望。他们一直这么评价我,而我对此深信不疑。在这个全民DotA的时代,我也不例外。我DotA玩的怎么样,我不好去评价,和我一起DotA的兄弟们是这么评价我的,"前期打得没的说!"邱涵说;"Gank打得没的说!"程龙说;

  9. Polarized quantum dot emission in electrohydrodynamic jet printed photonic crystals

    International Nuclear Information System (INIS)

    Tailored optical output, such as color purity and efficient optical intensity, are critical considerations for displays, particularly in mobile applications. To this end, we demonstrate a replica molded photonic crystal structure with embedded quantum dots. Electrohydrodynamic jet printing is used to control the position of the quantum dots within the device structure. This results in significantly less waste of the quantum dot material than application through drop-casting or spin coating. In addition, the targeted placement of the quantum dots minimizes any emission outside of the resonant enhancement field, which enables an 8× output enhancement and highly polarized emission from the photonic crystal structure

  10. Electric and Magnetic Interaction between Quantum Dots and Light

    DEFF Research Database (Denmark)

    Tighineanu, Petru

    a future challenge for the droplet-epitaxy technique. A multipolar theory of spontaneous emission from quantum dots is developed to explain the recent observation that In(Ga)As quantum dots break the dipole theory. The analysis yields a large mesoscopic moment, which contains magnetic-dipole and electric......-matter interaction of both electric and magnetic character. Our study demonstrates that In(Ga)As quantum dots lack parity symmetry and, as consequence, can be employed for locally probing the parity symmetry of complex photonic nanostructures. This opens the prospect for interfacing quantum dots with optical...

  11. Second-harmonic imaging of semiconductor quantum dots

    DEFF Research Database (Denmark)

    Østergaard, John Erland; Bozhevolnyi, Sergey I.; Pedersen, Kjeld;

    2000-01-01

    Resonant second-harmonic generation is observed at room temperature in reflection from self-assembled InAlGaAs quantum dots grown on a GaAs (001) substrate. The detected second-harmonic signal peaks at a pump wavelength of similar to 885 nm corresponding to the quantum-dot photoluminescence maxim...... observe that second-harmonic images of the quantum-dot surface structure show wavelength-dependent spatial variations. Imaging at different wavelength is used to demonstrate second-harmonic generation from the semiconductor quantum dots. (C) 2000 American Institute of Physics....

  12. SMM DotA大赛结束中国DotA战队囊括三甲

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    11月27至29日,国外著名DotA大赛Sendi Mutiara Multimedia Grand National DotA Tournament:Grand Firlals 2009(以下简称SMM09)在马来西亚马六甲州进行了为期三天的精彩大战.最终来自中国的三支战队sGty、cD、EHOME囊括三甲。成为SMM09的最大赢家。

  13. Emission switching in carbon dots coated CdTe quantum dots driving by pH dependent hetero-interactions

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Xiao; Wang, Hao; Yi, Qinghua; Wang, Yun; Cong, Shan; Zhao, Jie; Sun, Yinghui; Zou, Guifu, E-mail: zouguifu@suda.edu.cn, E-mail: jiexiong@uestc.edu.cn [College of Physics, Optoelectronics and Energy and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Qian, Zhicheng [School of Electronic and Information Engineering, Xi' an Jiaotong University, Xi' an 710049 (China); Huang, Jianwen; Xiong, Jie, E-mail: zouguifu@suda.edu.cn, E-mail: jiexiong@uestc.edu.cn [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China); Luo, Hongmei [Department of Chemical and Materials Engineering, New Mexico State University, Las Cruces, New Mexico 88003 (United States)

    2015-11-16

    Due to the different emission mechanism between fluorescent carbon dots and semiconductor quantum dots (QDs), it is of interest to explore the potential emission in hetero-structured carbon dots/semiconducting QDs. Herein, we design carbon dots coated CdTe QDs (CDQDs) and investigate their inherent emission. We demonstrate switchable emission for the hetero-interactions of the CDQDs. Optical analyses indicate electron transfer between the carbon dots and the CdTe QDs. A heterojunction electron process is proposed as the driving mechanism based on N atom protonation of the carbon dots. This work advances our understanding of the interaction mechanism of the heterostructured CDQDs and benefits the future development of optoelectronic nanodevices with new functionalities.

  14. Eléments traces dans le sérum des enfants malnutris et bien nourris vivants à Lubumbashi et Kawama dans un contexte d'un environnement de pollution minière

    Science.gov (United States)

    Musimwa, Aimée Mudekereza; Kanteng, Gray Wakamb; Kitoko, Hermann Tamubango; Luboya, Oscar Numbi

    2016-01-01

    Introduction La place des éléments traces métalliques essentiels en nutrition humaine ne peut plus être ignorée. Les déficits d'apports, les carences secondaires souvent sous – estimées, et les carences iatrogènes font le lit de pathologies telles que les infections et autres. D'où leurs dosages ont une importance particulière pour en évaluer la gravité et faciliter une prise en charge précoce ou améliorer le régime alimentaire. Cette étude a eu pour objectif de déterminer le profil sanguin en éléments traces (cuivre, sélénium, zinc, fer, chrome, cobalt, etc) chez les enfants malnutris et biens nourris dans un milieu minier à Lubumbashi. Méthodes Trois cents onze cas ont été colligés, 182 malnutris et 129 biens nourris, dans une étude descriptive transversale, effectuée de juillet 2013 à décembre 2014. Pour lequel un échantillonnage exhaustif a été réalisé. Le dosage des métaux dans le sérum s'est fait à l’ ICP-OES (spectrométrie de masse à plasma gon induit) au laboratoire de l'Office Congolais de Contrôle de Lubumbashi. Résultats Les oligoéléments essentiels (cuivre, zinc, sélénium et fer) se retrouvent à des concentrations très basses chez les enfants malnutris comme chez les biens nourris. L'arsenic, le cadmium, le magnésium et le manganèse se présentent à des concentrations normales par rapport aux valeurs de références chez les enfants biens nourris. L'antimoine, le chrome, le plomb et le cobalt se retrouvent élevés chez les malnutris et biens nourris. Le nickel est normal chez les malnutris et les biens nourris. Le magnésium, manganèse se sont présentés à des taux très bas chez les enfants malnutris. Conclusion Les enfants malnutris et biens nourris présentent une malnutrition aux oligo-éléments essentiels associés aux éléments traces métalliques. Ce qui permet de supposer qu'une carence en micronutriments essentiel favorise l'absorption des métaux lourds. PMID:27583075

  15. Conflictos por la herencia de bienes vinculados: Mujeres nobles pleiteando Conflicts for the inheritance of linked goods: Noble women going to law

    Directory of Open Access Journals (Sweden)

    Marcela Correa Barboza

    2012-12-01

    Full Text Available La casa, el parentesco, la clientela son vínculos que estructuran a conjuntos de individuos relacionados entre ellos, permitiéndoles actuar como agentes sociales colectivos. En las sociedades alto-modernas, de carácter patriarcal, las mujeres se encontraban supeditadas a la autoridad del varón, siendo éste quien actuaba socialmente, estableciendo diferentes vínculos entre familias, parientes, etc; relaciones a las que las mujeres quedaban sujetas en gran medida. Sin embargo, la historia de las mujeres ha mostrado que ellas tenían un accionar muy activo, eran capaces de intervenir en los vínculos ya existentes de manera decisiva, entablaban alianzas y promovían importantes redes de relaciones, que muchas veces encabezaban. En los últimos veinte años, se han puesto de relieve nuevas fuentes y nuevas categorías que enriquecen los estudios y propician otras formas de mirar la documentación. La utilización de la categoría género en el análisis ha permitido redimensionar el lugar de las mujeres en la historia. En los casos que presentaremos y en los temas que abordaremos, podremos observar las formas en que las mujeres de la muy alta nobleza actúan como verdaderas cabeza de linajes, defendiendo intereses propios, pero sobre todo colectivos - los de su familia-, buscando en los vericuetos legales las formas de conseguir cierto patrimonio, de mantenerlo en su círculo más cercano y, al mismo tiempo, de aumentarlo si consideran la posibilidad de acceder a nuevos bienes a través de herencias, compras, intercambios, etc.The house, kinship, the clientele are links that structure to sets of individuals related to each other, enabling them to act as collective social agents. In high-modern societies, the patriarchal nature, women were subject to male authority, this being who acted socially, establishing links between different families, relatives, etc., relations which women were subject to a great extent. However, women's history has

  16. The Electron-Hole Pair in a Single Quantum Dot and That in a Vertically Coupled Quantum Dot

    Institute of Scientific and Technical Information of China (English)

    XIE Wen-Fang; ZHU Wu

    2003-01-01

    The energy spectra of low-lying states of an exciton in a single and a vertically coupled quantum dots arestudied under the influence of a perpendicularly applied magnetic field. Calculations are made by using the method ofnumerical diagonalization of the Hamiltonian within the effective-mass approximation. We also calculated the bindingenergy of the ground and the excited states of an exciton in a single quantum dot and that in a vertically coupledquantum dot as a function of the dot radius for different values of the distance and the magnetic field strength.

  17. The Electron-Hole Pair in a Single Quantum Dot and That in a Vertically Coupled Quantum Dot

    Institute of Scientific and Technical Information of China (English)

    XIEWen-Fang; ZHUWu

    2003-01-01

    The energy spectra of low-lying states of an exciton in a single and a vertically coupled quantum dots are studied under the influence of a perpendicularly applied magnetic field. Calculations are made by using the method of numerical diagonalization of the Hamiltonian within the effective-mass approximation. We also calculated the binding energy of the ground and the excited states of an exciton in a single quantum dot and that in a vertically coupled quantum dot as a function of the dot radius for different vaJues of the distance and the magnetic field strength.

  18. Electron charging in epitaxial germanium quantum dots on silicon (100)

    Science.gov (United States)

    Ketharanathan, Sutharsan

    The electron charging behavior of self assembled epitaxial Ge quantum dots on Si(100) grown using molecular beam epitaxy has been studied. Ge quantum dots encapsulated in n-type Si matrix were incorporated into Schottky diodes to investigate their charging behavior using capacitance-voltage measurements. These experimental results were interpreted in the context of theoretical models to assess the degree of charge localization to the dot. Experiments involving Ge quantum dot growth, growth of Sb-doped Si and morphological evolution during encapsulation of the Ge dots during Si overgrowth were performed in order to optimize the conditions for obtaining distinct Ge quantum dot morphologies. This investigation included finding a suitable method to minimize Sb segregation while maintaining good dot epitaxy and overall crystal quality. Holes are confined to the Ge dots for which the valence band offsets are large (˜650 meV). Electrons are confined to the strained Si regions adjacent to the Ge quantum dots which have relatively smaller confinement potentials (˜100--150 meV). Experimentally, it was found that but and pyramid clusters in the range from 20--40 nm in diameter confine ˜1electron per dot while dome clusters in the range from 60--80 nm diameter confine ˜6--8 electrons per dot. Theoretical simulations predict that similar pyramid structures confine ˜0.4 electrons per dot and dome structures confine ˜2.2--3 electrons per dot. Even though the theory and the experimental results disagree due to various uncertainties and approximations, the ratio between theory and experiment agree remarkably well for both island types. We also investigated constructive three-dimensional nanolithography. Nanoscale Au rich dots and pure Ge dots were deposited on SiO2 and Si3N4 substrates by decomposing adsorbed precursors using a focused electron beam in an environmental transmission electron microscope. Dimethyl acetylacetonate gold was used for Au and digermane was used to

  19. Hybrid passivated colloidal quantum dot solids

    KAUST Repository

    Ip, Alex

    2012-07-29

    Colloidal quantum dot (CQD) films allow large-area solution processing and bandgap tuning through the quantum size effect. However, the high ratio of surface area to volume makes CQD films prone to high trap state densities if surfaces are imperfectly passivated, promoting recombination of charge carriers that is detrimental to device performance. Recent advances have replaced the long insulating ligands that enable colloidal stability following synthesis with shorter organic linkers or halide anions, leading to improved passivation and higher packing densities. Although this substitution has been performed using solid-state ligand exchange, a solution-based approach is preferable because it enables increased control over the balance of charges on the surface of the quantum dot, which is essential for eliminating midgap trap states. Furthermore, the solution-based approach leverages recent progress in metal:chalcogen chemistry in the liquid phase. Here, we quantify the density of midgap trap states in CQD solids and show that the performance of CQD-based photovoltaics is now limited by electrong-"hole recombination due to these states. Next, using density functional theory and optoelectronic device modelling, we show that to improve this performance it is essential to bind a suitable ligand to each potential trap site on the surface of the quantum dot. We then develop a robust hybrid passivation scheme that involves introducing halide anions during the end stages of the synthesis process, which can passivate trap sites that are inaccessible to much larger organic ligands. An organic crosslinking strategy is then used to form the film. Finally, we use our hybrid passivated CQD solid to fabricate a solar cell with a certified efficiency of 7.0%, which is a record for a CQD photovoltaic device. © 2012 Macmillan Publishers Limited. All rights reserved.

  20. Nonvolatile Quantum Dot Gate Memory (NVQDM): Tunneling Rate from Quantum Well Channel to Quantum Dot Gate

    Science.gov (United States)

    Hasaneen, El-Sayed; Heller, Evan; Bansal, Rajeev; Jain, Faquir

    2003-10-01

    In this paper, we compute the tunneling of electrons in a nonvolatile quantum dot memory (NVQDM) cell during the WRITE operation. The transition rate of electrons from a quantum well channel to the quantum dots forming the floating gate is calculated using a recently reported method by Chuang et al.[1]. Tunneling current is computed based on transport of electrons from the channel to the floating quantum dots. The maximum number of electrons on a dot is calculated using surface electric field and break down voltage of the tunneling dielectric material. Comparison of tunneling for silicon oxide and high-k dielectric gate insulators is also described. Capacitance-Voltage characteristics of a NVQDM device are calculated by solving the Schrodinger and Poisson equations self-consistently. In addition, the READ operation of the memory has been investigated analytically. Results for 70 nm channel length Si NVQDMs are presented. Threshold voltage is calculated including the effect of the charge on nanocrystal quantum dots. Current-voltage characteristics are obtained using BSIM3v3 model [2-3]. This work is supported by Office of Navel Research (N00014210883, Dr. D. Purdy, Program Monitor), Connecticut Innovations Inc./TranSwitch (CII # 00Y17), and National Science Foundation (CCR-0210428) grants. [1] S. L. Chuang and N. Holonyak, Appl. Phys. Lett., 80, pp. 1270, 2002. [2] Y. Chen et. al., BSIM3v3 Manual, Elect. Eng. and Comp. Dept., U. California, Berkeley, CA, 1996. [3] W. Liu, MOSFET Models for SPICE Simulation, John Wiley & Sons, Inc., 2001.

  1. Quantum dot density studies for quantum dot intermediate band solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Thomassen, Sedsel Fretheim; Zhou, Dayong; Vitelli, Stefano; Mayani, Maryam Gholami; Fimland, Bjoern-Ove; Reenaas, Turid Worren

    2010-07-01

    Quantum dots (QDs) have been an active area of research for many years and have been implemented in several applications, such as lasers and detectors. During the last years, some attempts have been made to increase the absorption and efficiency of solar cells by inserting QDs into the intrinsic region of pin solar cells. So far, these attempts have been successful in increasing the absorption, but not the cell efficiency. There are probably several reasons for this lack of efficiency increase, but we believe that one important reason is the low density of the implemented QDs. In this work, samples of single layer InAs QDs on n-GaAs(001) substrates have been grown by molecular beam epitaxy (MBE) and we have performed a systematic study of how deposition parameters affect the QD density. The aim is to achieve densities > 1011 cm-2. The nominal substrate temperature (360 - 500 deg. C), the InAs growth rate (0.085 - 1 ML/s) and thickness (2.0 - 2.8 ML) have been varied in a systematic way for two different deposition methods of InAs, i.e. continuous deposition or deposition with interruptions. In addition, we have for the continuous growth samples also varied the As-flux (0.5 - 6 centre dot10-6 torr). Scanning electron microscopy (SEM) has been the main characterization method to determine quantum dot sizes and densities, and atomic force microscopy (AFM) has been used for evaluation of the quantum dot heights. We find that the QD density increases with reduced growth temperature and that it is higher for samples grown continuously than for samples grown with growth interruptions. The homogeneity is also strongly affected by temperature, InAs deposition method and the As-flux. We have observed QD densities as high as 2.5 centre dot1011 cm-2 for the samples grown at the lowest growth temperatures. (Author)

  2. Ultra-bright alkylated graphene quantum dots

    Science.gov (United States)

    Feng, Lan; Tang, Xing-Yan; Zhong, Yun-Xin; Liu, Yue-Wen; Song, Xue-Huan; Deng, Shun-Liu; Xie, Su-Yuan; Yan, Jia-Wei; Zheng, Lan-Sun

    2014-10-01

    Highly efficient and stable photoluminescence (PL) are urgently desired for graphene quantum dots (GQDs) to facilitate their prospective applications as optical materials. Here, we report the facile and straightforward synthesis of alkylated graphene quantum dots (AGQDs) via the solvothermal reaction of propagatively alkylated graphene sheets (PAGenes). In contrast to most GQDs reported so far, the synthesized AGQDs process pH-independent and ultra-bright PL with a relative quantum yield of up to 65%. Structural and chemical composition characterization demonstrated that the synthesized AGQDs are nearly oxygen-defect-free with alkyl groups decorated on edges and basal plane, which may contribute to their greatly improved pH tolerance and high quantum efficiency. The photocatalytic performance of AGQDs-P25 nanocomposites was evaluated by the degradation of Rhodamine B under visible light. The photocatalytic rate is ca. 5.9 times higher than that of pure P25, indicating that AGQDs could harness the visible spectrum of sunlight for energy conversion or environmental therapy.Highly efficient and stable photoluminescence (PL) are urgently desired for graphene quantum dots (GQDs) to facilitate their prospective applications as optical materials. Here, we report the facile and straightforward synthesis of alkylated graphene quantum dots (AGQDs) via the solvothermal reaction of propagatively alkylated graphene sheets (PAGenes). In contrast to most GQDs reported so far, the synthesized AGQDs process pH-independent and ultra-bright PL with a relative quantum yield of up to 65%. Structural and chemical composition characterization demonstrated that the synthesized AGQDs are nearly oxygen-defect-free with alkyl groups decorated on edges and basal plane, which may contribute to their greatly improved pH tolerance and high quantum efficiency. The photocatalytic performance of AGQDs-P25 nanocomposites was evaluated by the degradation of Rhodamine B under visible light. The

  3. Quantum dot loaded immunomicelles for tumor imaging

    Directory of Open Access Journals (Sweden)

    Levchenko Tatyana

    2010-10-01

    Full Text Available Abstract Background Optical imaging is a promising method for the detection of tumors in animals, with speed and minimal invasiveness. We have previously developed a lipid coated quantum dot system that doubles the fluorescence of PEG-grafted quantum dots at half the dose. Here, we describe a tumor-targeted near infrared imaging agent composed of cancer-specific monoclonal anti-nucleosome antibody 2C5, coupled to quantum dot (QD-containing polymeric micelles, prepared from a polyethylene glycol/phosphatidylethanolamine (PEG-PE conjugate. Its production is simple and involves no special equipment. Its imaging potential is great since the fluorescence intensity in the tumor is twofold that of non-targeted QD-loaded PEG-PE micelles at one hour after injection. Methods Para-nitrophenol-containing (5% PEG-PE quantum dot micelles were produced by the thin layer method. Following hydration, 2C5 antibody was attached to the PEG-PE micelles and the QD-micelles were purified using dialysis. 4T1 breast tumors were inoculated subcutaneously in the flank of the animals. A lung pseudometastatic B16F10 melanoma model was developed using tail vein injection. The contrast agents were injected via the tail vein and mice were depilated, anesthetized and imaged on a Kodak Image Station. Images were taken at one, two, and four hours and analyzed using a methodology that produces normalized signal-to-noise data. This allowed for the comparison between different subjects and time points. For the pseudometastatic model, lungs were removed and imaged ex vivo at one and twenty four hours. Results The contrast agent signal intensity at the tumor was double that of the passively targeted QD-micelles with equally fast and sharply contrasted images. With the side views of the animals only tumor is visible, while in the dorsal view internal organs including liver and kidney are visible. Ex vivo results demonstrated that the agent detects melanoma nodes in a lung

  4. Fano-Rashba effect in quantum dots

    International Nuclear Information System (INIS)

    We consider the electronic transport through a Rashba quantum dot coupled to ferromagnetic leads. We show that the interference of localized electron states with resonant electron states leads to the appearance of the Fano-Rashba effect. This effect occurs due to the interference of bound levels of spin-polarized electrons with the continuum of electronic states with an opposite spin polarization. We investigate this Fano-Rashba effect as a function of the applied magnetic field and Rashba spin-orbit coupling

  5. Cotunneling effects in GaAs vertical double quantum dot

    OpenAIRE

    Badrutdinov, A. O.; Huang, S. M.; Kono, K; Ono, K.; Tayurskii, D. A.

    2010-01-01

    We observed lifting of Coulomb blockade in GaAs vertical double quantum dot with low potential barriers, induced by cotunneling mechanisms at dilution fridge temperature of 10 mK. Several distinct features were observed, compared to single dot case, and appropriate explanation for them was given

  6. A Multi-Chanel Speckle Imaging for the DOT

    NARCIS (Netherlands)

    Sütterlin, P.; Hammerschlag, R.H.; Bettonvil, F.C.M.; Rutten, R.J.; Skomorovsky, V.I.; Domyshev, G.N.

    2001-01-01

    The Dutch Open Telescope (DOT) had its initial observing campaighn in September 1999. Alhough only a simple video system was used, the results demonstrated the excellent high-resolution capabilities of the combination of the open-teloscope concept, the DOT optics, the remaining image degradation due

  7. High-resolution photoluminescence studies of single semiconductor quantum dots

    DEFF Research Database (Denmark)

    Leosson, Kristjan; Østergaard, John Erland; Jensen, Jacob Riis;

    2000-01-01

    Semiconductor quantum dots, especially those formed by self-organized growth, are considered a promising material system for future optical devices [1] and the optical properties of quantum dot ensembles have been investigated in detail over the past years. Recently, considerable interest has...

  8. DOE evaluation document for DOT 7A Type A packaging

    International Nuclear Information System (INIS)

    This document, DOE Evaluation Document for DOT 7A Type A Packaging, March 1987, presents approximately 100 different packagings which have been determined to meet the requirements for a DOT Spec 7A Type A packaging (49 CFR 178.350) and satisfies the requirements of 49 CFR 174.315(a) concerning the requirements for a document

  9. 49 CFR 15.15 - SSI disclosed by DOT.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 1 2010-10-01 2010-10-01 false SSI disclosed by DOT. 15.15 Section 15.15 Transportation Office of the Secretary of Transportation PROTECTION OF SENSITIVE SECURITY INFORMATION § 15.15 SSI... containing SSI are not available for public inspection or copying, nor does DOT release such records...

  10. Transport through Zero-Dimensional States in a Quantum Dot

    NARCIS (Netherlands)

    Kouwenhoven, Leo P.; Wees, Bart J. van; Harmans, Kees J.P.M.; Williamson, John G.

    1990-01-01

    We have studied the electron transport through zero-dimensional (0D) states. 0D states are formed when one-dimensional edge channels are confined in a quantum dot. The quantum dot is defined in a two-dimensional electron gas with a split gate technique. To allow electronic transport, connection to t

  11. Negative Trions Trapped by a Spherical Parabolic Quantum Dot

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    In this paper, a negatively charged exciton trapped by a spherical parabolic quantum dot has been investigated. The energy spectra of low-lying states are calculated by means of matrix diagonalization. The important feature of the low-lying states of the negatively charged excitons in a spherical quantum dot is obtained via an analysis of the energy spectra.

  12. Ultrafast gain and index dynamics in quantum dot amplifiers

    DEFF Research Database (Denmark)

    Borri, Paola; Langbein, Wolfgang; Mørk, Jesper;

    1999-01-01

    The ultrafast dynamics of gain and refractive index in an InAs/GaAs quantum dot amplifier are investigated at room temperature. The gain is observed to recover with a 90 fs time constant, ruling out problems of slow carrier capture into the dots, and making this component promising for high...

  13. Electronic properties of assemblies of zno quantum dots

    NARCIS (Netherlands)

    Roest, Aarnoud Laurens

    2003-01-01

    Electron transport in an assembly of ZnO quantum dots has been studied using an electrochemically gated transistor. The electron mobility shows a step-wise increase as a function of the electron occupation per quantum dot. When the occupation number is below two, transport occurs by tunnelling betwe

  14. Electron Transport in Quantum Dots and Heat Transport in Molecules

    DEFF Research Database (Denmark)

    Kirsanskas, Gediminas

    and to perform electrical transport experiments at temperatures below one Kelvin (1 K), and thus to address such question. In this thesis we are concerned with the theoretical description of one kind of such devices called quantum dots. As the name suggest a quantum dot is a system where particles are confined...

  15. LUMINESCENCE OF CADMIUM SULFIDE QUANTUM DOTS IN FLUOROPHOSPHATE GLASSES

    Directory of Open Access Journals (Sweden)

    Z. O. Lipatova

    2015-03-01

    Full Text Available Cadmium sulfide quantum dots are perspective materials in optics, medicine, biology and optoelectronics. Fluorophosphate glasses, doped with cadmium sulfide quantum dots, were examined in the paper. Heat treatment led to the formation of quantum dots with diameters equal to 2.8 nm, 3.0 nm and 3.8 nm. In view of such changes in the quantum dots size the fundamental absorption edge shift and the luminescence band are being displaced to the long wavelengths. Luminescence lifetime has been found to be dependent on the registration wavelength in the range from 450 to 700 nm. Obtained fluorophosphate glasses with CdS quantum dots can find their application as fluorescent materials with intensive luminescence band and long excited-state natural lifetime.

  16. Synthesis of biocompatible multicolor luminescent carbon dots for bioimaging applications

    Directory of Open Access Journals (Sweden)

    Nagaprasad Puvvada, B N Prashanth Kumar, Suraj Konar, Himani Kalita, Mahitosh Mandal and Amita Pathak

    2012-01-01

    Full Text Available Water-soluble carbon dots (C-dots were prepared through microwave-assisted pyrolysis of an aqueous solution of dextrin in the presence of sulfuric acid. The C-dots produced showed multicolor luminescence in the entire visible range, without adding any surface-passivating agent. X-ray diffraction and Fourier transform infrared spectroscopy studies revealed the graphitic nature of the carbon and the presence of hydrophilic groups on the surface, respectively. The formation of uniformly distributed C-dots and their luminescent properties were, respectively, revealed from transmission electron microscopy and confocal laser scanning microscopy. The biocompatible nature of C-dots was confirmed by a cytotoxicity assay on MDA-MB-468 cells and their cellular uptake was assessed through a localization study.

  17. Resonance fluorescence from a telecom-wavelength quantum dot

    CERN Document Server

    Al-Khuzheyri, R; Huwer, J; Santana, T S; Szymanska, J Skiba-; Felle, M; Ward, M B; Stevenson, R M; Farrer, I; Tanner, M G; Hadfield, R H; Ritchie, D A; Shields, A J; Gerardot, B D

    2016-01-01

    We report on resonance fluorescence from a single quantum dot emitting at telecom wavelengths. We perform high-resolution spectroscopy and observe the Mollow triplet in the Rabi regime--a hallmark of resonance fluorescence. The measured resonance-fluorescence spectra allow us to rule out pure dephasing as a significant decoherence mechanism in these quantum dots. Combined with numerical simulations, the experimental results provide robust characterisation of charge noise in the environment of the quantum dot. Resonant control of the quantum dot opens up new possibilities for on-demand generation of indistinguishable single photons at telecom wavelengths as well as quantum optics experiments and direct manipulation of solid-state qubits in telecom-wavelength quantum dots.

  18. Single-electron Spin Resonance in a Quadruple Quantum Dot

    Science.gov (United States)

    Otsuka, Tomohiro; Nakajima, Takashi; Delbecq, Matthieu R.; Amaha, Shinichi; Yoneda, Jun; Takeda, Kenta; Allison, Giles; Ito, Takumi; Sugawara, Retsu; Noiri, Akito; Ludwig, Arne; Wieck, Andreas D.; Tarucha, Seigo

    2016-08-01

    Electron spins in semiconductor quantum dots are good candidates of quantum bits for quantum information processing. Basic operations of the qubit have been realized in recent years: initialization, manipulation of single spins, two qubit entanglement operations, and readout. Now it becomes crucial to demonstrate scalability of this architecture by conducting spin operations on a scaled up system. Here, we demonstrate single-electron spin resonance in a quadruple quantum dot. A few-electron quadruple quantum dot is formed within a magnetic field gradient created by a micro-magnet. We oscillate the wave functions of the electrons in the quantum dots by applying microwave voltages and this induces electron spin resonance. The resonance energies of the four quantum dots are slightly different because of the stray field created by the micro-magnet and therefore frequency-resolved addressable control of each electron spin resonance is possible.

  19. RKKY interaction in a chirally coupled double quantum dot system

    Energy Technology Data Exchange (ETDEWEB)

    Heine, A. W.; Tutuc, D.; Haug, R. J. [Institut für Festkörperphysik, Leibniz Universität Hannover, Appelstr. 2, 30167 Hannover (Germany); Zwicknagl, G. [Institut für Mathematische Physik, TU Braunschweig, Mendelssohnstr. 3, 38106 Braunschweig (Germany); Schuh, D. [Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Universitätstr. 31, 93053 Regensburg (Germany); Wegscheider, W. [Laboratorium für Festkörperphysik, ETH Zürich, Schafmattstr. 16, 8093 Zürich, Switzerland and Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Universitätstr. 31, 93053 Regens (Germany)

    2013-12-04

    The competition between the Kondo effect and the Ruderman-Kittel-Kasuya-Yoshida (RKKY) interaction is investigated in a double quantum dots system, coupled via a central open conducting region. A perpendicular magnetic field induces the formation of Landau Levels which in turn give rise to the so-called Kondo chessboard pattern in the transport through the quantum dots. The two quantum dots become therefore chirally coupled via the edge channels formed in the open conducting area. In regions where both quantum dots exhibit Kondo transport the presence of the RKKY exchange interaction is probed by an analysis of the temperature dependence. The thus obtained Kondo temperature of one dot shows an abrupt increase at the onset of Kondo transport in the other, independent of the magnetic field polarity, i.e. edge state chirality in the central region.

  20. Double Rashba Quantum Dots Ring as a Spin Filter

    Directory of Open Access Journals (Sweden)

    Chi Feng

    2008-01-01

    Full Text Available AbstractWe theoretically propose a double quantum dots (QDs ring to filter the electron spin that works due to the Rashba spin–orbit interaction (RSOI existing inside the QDs, the spin-dependent inter-dot tunneling coupling and the magnetic flux penetrating through the ring. By varying the RSOI-induced phase factor, the magnetic flux and the strength of the spin-dependent inter-dot tunneling coupling, which arises from a constant magnetic field applied on the tunneling junction between the QDs, a 100% spin-polarized conductance can be obtained. We show that both the spin orientations and the magnitude of it can be controlled by adjusting the above-mentioned parameters. The spin filtering effect is robust even in the presence of strong intra-dot Coulomb interactions and arbitrary dot-lead coupling configurations.

  1. Silicon quantum dots: fine-tuning to maturity

    Science.gov (United States)

    Morello, Andrea

    2015-12-01

    Quantum dots in semiconductor heterostructures provide one of the most flexible platforms for the study of quantum phenomena at the nanoscale. The surging interest in using quantum dots for quantum computation is forcing researchers to rethink fabrication and operation methods, to obtain highly tunable dots in spin-free host materials, such as silicon. Borselli and colleagues report in Nanotechnology the fabrication of a novel Si/SiGe double quantum dot device, which combines an ultra-low disorder Si/SiGe accumulation-mode heterostructure with a stack of overlapping control gates, ensuring tight confining potentials and exquisite tunability. This work signals the technological maturity of silicon quantum dots, and their readiness to be applied to challenging projects in quantum information science.

  2. Interaction of porphyrins with CdTe quantum dots

    International Nuclear Information System (INIS)

    Porphyrins may be used as photosensitizers for photodynamic therapy, photocatalysts for organic pollutant dissociation, agents for medical imaging and diagnostics, applications in luminescence and electronics. The detection of porphyrins is significantly important and here the interaction of protoporphyrin-IX (PPIX) with CdTe quantum dots was studied. It was observed that the luminescence of CdTe quantum dots was quenched dramatically in the presence of PPIX. When CdTe quantum dots were embedded into silica layers, almost no quenching by PPIX was observed. This indicates that PPIX may interact and alter CdTe quantum dots and thus quench their luminescence. The oxidation of the stabilizers such as thioglycolic acid (TGA) as well as the nanoparticles by the singlet oxygen generated from PPIX is most likely responsible for the luminescence quenching. The quenching of quantum dot luminescence by porphyrins may provide a new method for photosensitizer detection.

  3. DotFETs: MOSFETs strained by a Single SiGE dot in a Low-Temperature ELA Technology

    NARCIS (Netherlands)

    Biasotto, C.

    2011-01-01

    The work presented in this thesis was performed in the context of the European Sixth Framework Program FP6 project “Disposable Dot Field Effect Transistor for High Speed Si Integrated Circuits”, referred to as the D-DotFET project. The project had the goal of realizing strain-enhanced mobility in CM

  4. La centration sur le processus du changement : l'apport de l'intervention systémique à l'amélioration du bien-être au travail

    OpenAIRE

    Althaus, Virginie; Grosjean, Vincent; Brangier, Eric

    2013-01-01

    International audience; Pour intervenir sur la santé et le bien-être au travail, il est souvent d'usage de recourir à des méthodes centrées diagnostic, au sein desquelles une compréhension fine de la situation précède l'action. Des auteurs soulignent néanmoins les limites de cette approche lorsqu'il s'agit de mobiliser les connaissances accumulées sur la situation de travail en vue de la transformer. Par contraste, les interventions affiliées au paradigme systémique se focalisent sur le proce...

  5. Efecto del subprograma de apoyo a los proyectos de inversión rural (PAPIR) en productores que recibieron bienes de capital durante el periodo 2002-2007 en la Región Libres, Puebla, México.

    OpenAIRE

    Soto Reyes, Vianey

    2012-01-01

    El Subprograma de Apoyo a los Proyectos de Inversión Rural (PAPIR), fue un programa diseñado para fomentar la inversión en bienes de capital de la población rural elegible a través del apoyo para la puesta en marcha de proyectos productivos que posibiliten la aplicación de tecnologías apropiadas, la reconversión productiva, el acopio, acondicionamiento y transformación para fortalecer la comercialización de la producción primaria, la generación de empleo rural y de servicios, así como su posi...

  6. Salud e Internet o cómo conseguir pacientes crónicos bien informados y autónomos: el caso del EAP Mataró-6 (Barcelona, Cataluña)

    OpenAIRE

    Boté, Clara; Vall Casas, Aurora

    2012-01-01

    La consolidación progresiva del uso de las TIC en la sociedad actual así como el libre acceso a gran cantidad de información sobre salud en Internet, favorecen la aparición de pacientes activos y colaboradores. La relación "profesional sanitario-paciente" está evolucionando hacia un nuevo modelo en el cual se proporciona información adecuada y de calidad para conseguir pacientes expertos, bien informados y autónomos. En Cataluña, el personal de enfermería de atención primaria desarrolla funci...

  7. Aproximación a la lectura de bienes patrimonializados de la arquitectura racional del s.XX desde la “Dialéctica de la mirada” de Walter Benjamin

    OpenAIRE

    Cuello, Juan Nicolás

    2010-01-01

    En el marco del estudio de las posibles dimensiones epistemológicas del arte, lo que pretendo en este trabajo es abordar una aproximación a las consideraciones que se podrían realizar acerca de la arquitectura moderna o racional, y sobretodo aproximarme a una lectura de esta propuesta estilística desde la metodología desarrollada por Benjamin en su investigación sobre los Pasajes de Paris, conocida como Dialéctica de la mirada. Para ello tomare como ejemplos paradigmáticos dos bienes que son ...

  8. Aplicaciones de la tecnología de microondas a la desinsectación en los sectores: Cárnico y de restauración de bienes culturales

    OpenAIRE

    Zona Ortiz, Angela Tatiana

    2008-01-01

    Esta investigación amplia el campo de aplicación para el calor producido por las microondas en el área de desinsectación dentro de los sectores cárnico y de restauración de bienes culturales. Estableciendo un procedimiento inicial de aplicación que permita la conservación del material a desinsectar (jamón curado y madera), mientras se eliminan los agentes contaminantes (ácaros y carcoma). El objetivo que se persigue es la desinsectación segura, no invasiva y medioambientalmente limpia. La...

  9. Ivonne Farah H. / Luciano Vasapollo (Coordinadores), Vivir Bien: ¿Paradigma no capitalista?, Universidad Mayor de San Andrés(CIDES-UMSA) y Departamento de Economía de la Universidad de Roma La Sapienza, 2011, 437 p.

    OpenAIRE

    Perea Sandoval, Carlos

    2013-01-01

    La humanidad se encuentra en una constante búsqueda por construir una ética que permita hacer realidad el re-ligarse con el futuro, lo cual implica generar una convivencia recíproca con la naturaleza y las demás formas de vida, en el camino de la ética del bien común. La construcción de este modelo ético se constituye en una prioridad ya que desde el mismo es posible determinar caminos de acción, que a partir de una postura social y de apoyo mutuo, se concrete en alternativas para enfrentar e...

  10. Tercer Premio del I Concurso de monólogos científicos de la Facultad de Ciencias del Mar y Ambientales. Saber comer para crecer muy bien. La teoría endosimbiótica

    OpenAIRE

    Rodríguez López, Jaime; Cabrera Castro, Remedios; López López, José Antonio; Albendín García, Gemma

    2015-01-01

    La teoría endosimbiótica fue propuesta por Lynn Margulis en 1967 y como tantas otras al principio no fue bien valorada por los científicos. Esta teoría plantea esencialmente que algunos de los orgánulos de las células eucariotas, en particular las mitocondrias y los plastos, fueron en su momento organismos procariontes de vida libre (bacterias), que probablemente tras haber sido fagocitadas no fueron digeridas llegando a formar parte y creando una relación dependiente de la célula que las fag...

  11. La participación como bien de consumo : una aproximación conceptual a las formas de implicación de los usuarios en proyectos audiovisuales colaborativos

    OpenAIRE

    Roig Telo, Antoni

    2010-01-01

    Este artículo centra su atención en el concepto de participación, ampliamente utilizado —y también discutido— para hacer referencia a la implicación de los usuarios en la creación de contenidos audiovisuales en Internet. Particularmente, nos centraremos en la noción de participación de los públicos en el diseño, desarrollo y difusión de productos audiovisuales complejos, como por ejemplo largometrajes, webseries o proyectos ‘crossmedia’. Si bien la mayor parte del debate académico sobre la ca...

  12. Nano-laser on silicon quantum dots

    Science.gov (United States)

    Huang, Wei-Qi; Liu, Shi-Rong; Qin, Chao-Jian; Lü, Quan; Xu, Li

    2011-04-01

    A new conception of nano-laser is proposed in which depending on the size of nano-clusters (silicon quantum dots (QD)), the pumping level of laser can be tuned by the quantum confinement (QC) effect, and the population inversion can be formed between the valence band and the localized states in gap produced from the surface bonds of nano-clusters. Here we report the experimental demonstration of nano-laser on silicon quantum dots fabricated by nanosecond pulse laser. The peaks of stimulated emission are observed at 605 nm and 693 nm. Through the micro-cavity of nano-laser, a full width at half maximum of the peak at 693 nm can reach to 0.5 nm. The theoretical model and the experimental results indicate that it is a necessary condition for setting up nano-laser that the smaller size of QD (d nano-laser will be limited in the range of 1.7-2.3 eV generally due to the position of the localized states in gap, which is in good agreement between the experiments and the theory.

  13. Colloidal quantum dot light-emitting devices.

    Science.gov (United States)

    Wood, Vanessa; Bulović, Vladimir

    2010-01-01

    Colloidal quantum dot light-emitting devices (QD-LEDs) have generated considerable interest for applications such as thin film displays with improved color saturation and white lighting with a high color rendering index (CRI). We review the key advantages of using quantum dots (QDs) in display and lighting applications, including their color purity, solution processability, and stability. After highlighting the main developments in QD-LED technology in the past 15 years, we describe the three mechanisms for exciting QDs - optical excitation, Förster energy transfer, and direct charge injection - that have been leveraged to create QD-LEDs. We outline the challenges facing QD-LED development, such as QD charging and QD luminescence quenching in QD thin films. We describe how optical downconversion schemes have enabled researchers to overcome these challenges and develop commercial lighting products that incorporate QDs to achieve desirable color temperature and a high CRI while maintaining efficiencies comparable to inorganic white LEDs (>65 lumens per Watt). We conclude by discussing some current directions in QD research that focus on achieving higher efficiency and air-stable QD-LEDs using electrical excitation of the luminescent QDs. PMID:22110863

  14. Colloidal quantum dot light-emitting devices

    Directory of Open Access Journals (Sweden)

    Vanessa Wood

    2010-07-01

    Full Text Available Colloidal quantum dot light-emitting devices (QD-LEDs have generated considerable interest for applications such as thin film displays with improved color saturation and white lighting with a high color rendering index (CRI. We review the key advantages of using quantum dots (QDs in display and lighting applications, including their color purity, solution processability, and stability. After highlighting the main developments in QD-LED technology in the past 15 years, we describe the three mechanisms for exciting QDs – optical excitation, Förster energy transfer, and direct charge injection – that have been leveraged to create QD-LEDs. We outline the challenges facing QD-LED development, such as QD charging and QD luminescence quenching in QD thin films. We describe how optical downconversion schemes have enabled researchers to overcome these challenges and develop commercial lighting products that incorporate QDs to achieve desirable color temperature and a high CRI while maintaining efficiencies comparable to inorganic white LEDs (>65 lumens per Watt. We conclude by discussing some current directions in QD research that focus on achieving higher efficiency and air-stable QD-LEDs using electrical excitation of the luminescent QDs.

  15. Study of metallothionein-quantum dots interactions.

    Science.gov (United States)

    Tmejova, Katerina; Hynek, David; Kopel, Pavel; Krizkova, Sona; Blazkova, Iva; Trnkova, Libuse; Adam, Vojtech; Kizek, Rene

    2014-05-01

    Nanoparticles have gained increasing interest in medical and in vivo applications. Metallothionein (MT) is well known as a maintainer of metal ions balance in intracellular space. This is due to high affinity of this protein to any reactive species including metals and reactive oxygen species. The purpose of this study was to determine the metallothionein-quantum dots interactions that were investigated by spectral and electrochemical techniques. CuS, CdS, PbS, and CdTe quantum dots (QDs) were analysed. The highest intensity was shown for CdTe, than for CdS measured by fluorescence. These results were supported by statistical analysis and considered as significant. Further, these interactions were analysed using gel electrophoresis, where MT aggregates forming after interactions with QDs were detected. Using differential pulse voltammetry Brdicka reaction, QDs and MT were studied. This method allowed us to confirm spectral results and, moreover, to observe the changes in MT structure causing new voltammetric peaks called X and Y, which enhanced with the prolonged time of interaction up to 6 h.

  16. Using quantum dot photoluminescence for load detection

    Science.gov (United States)

    Moebius, M.; Martin, J.; Hartwig, M.; Baumann, R. R.; Otto, T.; Gessner, T.

    2016-08-01

    We propose a novel concept for an integrable and flexible sensor capable to visualize mechanical impacts on lightweight structures by quenching the photoluminescence (PL) of CdSe quantum dots. Considering the requirements such as visibility, storage time and high optical contrast of PL quenching with low power consumption, we have investigated a symmetrical and an asymmetrical layer stack consisting of semiconductor organic N,N,N',N'-Tetrakis(3-methylphenyl)-3,3'-dimethylbenzidine (HMTPD) and CdSe quantum dots with elongated CdS shell. Time-resolved series of PL spectra from layer stacks with applied voltages of different polarity and simultaneous observation of power consumption have shown that a variety of mechanisms such as photo-induced charge separation and charge injection, cause PL quenching. However, mechanisms such as screening of external field as well as Auger-assisted charge ejection is working contrary to that. Investigations regarding the influence of illumination revealed that the positive biased asymmetrical layer stack is the preferred sensor configuration, due to a charge carrier injection at voltages of 10 V without the need of coincident illumination.

  17. Excitation transfer in stacked quantum dot chains

    International Nuclear Information System (INIS)

    Stacked InAs quantum dot chains (QDCs) on InGaAs/GaAs cross-hatch pattern (CHP) templates yield a rich emission spectrum with an unusual carrier transfer characteristic compared to conventional quantum dot (QD) stacks. The photoluminescent spectra of the controlled, single QDC layer comprise multiple peaks from the orthogonal QDCs, the free-standing QDs, the CHP, the wetting layers and the GaAs substrate. When the QDC layers are stacked, employing a 10 nm GaAs spacer between adjacent QDC layers, the PL spectra are dominated by the top-most stack, indicating that the QDC layers are nominally uncoupled. Under high excitation power densities when the high-energy peaks of the top stack are saturated, however, low-energy PL peaks from the bottom stacks emerge as a result of carrier transfers across the GaAs spacers. These unique PL signatures contrast with the state-filling effects in conventional, coupled QD stacks and serve as a means to quickly assess the presence of electronic coupling in stacks of dissimilar-sized nanostructures. (paper)

  18. Quantum Computer Using Coupled Quantum Dot Molecules

    CERN Document Server

    Wu, N J; Natori, A; Yasunaga, H; Wu*, Nan-Jian

    1999-01-01

    We propose a method for implementation of a quantum computer using artificial molecules. The artificial molecule consists of two coupled quantum dots stacked along z direction and one single electron. One-qubit and two-qubit gates are constructed by one molecule and two coupled molecules, respectively.The ground state and the first excited state of the molecule are used to encode the |0> and |1> states of a qubit. The qubit is manipulated by a resonant electromagnetic wave that is applied directly to the qubit through a microstrip line. The coupling between two qubits in a quantum controlled NOT gate is switched on (off) by floating (grounding) the metal film electrodes. We study the operations of the gates by using a box-shaped quantum dot model and numerically solving a time-dependent Schridinger equation, and demonstrate that the quantum gates can perform the quantum computation. The operating speed of the gates is about one operation per 4ps. The reading operation of the output of the quantum computer can...

  19. Kondo effects in triangular triple quantum dots

    Science.gov (United States)

    Oguri, Akira; Numata, Takahide; Nisikawa, Yunori; Hewson, A. C.

    2009-03-01

    We study the conductance through a triangular triple quantum dot, which is connected to two noninteracting leads, using the numerical renormalization group (NRG). It is found that the system shows a variety of Kondo effects depending on the filling of the triangle. The SU(4) Kondo effect occurs at half-filling, and a sharp conductance dip due to a phase lapse appears in the gate-voltage dependence. Furthermore, when four electrons occupy the three sites on average, a local S=1 moment, which is caused by the Nagaoka mechanism, is induced along the triangle. The temperature dependence of the entropy and spin susceptibility of the triangle shows that this moment is screened by the conduction electrons via two separate stages at different temperatures. The two-terminal and four-terminal conductances show a clear difference at the gate voltages, where the SU(4) or the S=1 Kondo effects occur[1]. We will also discuss effects of deformations of the triangular configuration, caused by the inhomogeneity in the inter-dot couplings and in the gate voltages. [4pt] [1] T.Numata, Y.Nisikawa, A.Oguri, and A.C.Hewson: arXiv:0808.3496.

  20. Polymersomes containing quantum dots for cellular imaging

    Directory of Open Access Journals (Sweden)

    Camblin M

    2014-05-01

    Full Text Available Marine Camblin,1 Pascal Detampel,1 Helene Kettiger,1 Dalin Wu,2 Vimalkumar Balasubramanian,1,* Jörg Huwyler1,*1Division of Pharmaceutical Technology, 2Department of Chemistry, University of Basel, Basel, Switzerland*These authors contributed equally to this workAbstract: Quantum dots (QDs are highly fluorescent and stable probes for cellular and molecular imaging. However, poor intracellular delivery, stability, and toxicity of QDs in biological compartments hamper their use in cellular imaging. To overcome these limitations, we developed a simple and effective method to load QDs into polymersomes (Ps made of poly(dimethylsiloxane-poly(2-methyloxazoline (PDMS-PMOXA diblock copolymers without compromising the characteristics of the QDs. These Ps showed no cellular toxicity and QDs were successfully incorporated into the aqueous compartment of the Ps as confirmed by transmission electron microscopy, fluorescence spectroscopy, and fluorescence correlation spectroscopy. Ps containing QDs showed colloidal stability over a period of 6 weeks if stored in phosphate-buffered saline (PBS at physiological pH (7.4. Efficient intracellular delivery of Ps containing QDs was achieved in human liver carcinoma cells (HepG2 and was visualized by confocal laser scanning microscopy (CLSM. Ps containing QDs showed a time- and concentration-dependent uptake in HepG2 cells and exhibited better intracellular stability than liposomes. Our results suggest that Ps containing QDs can be used as nanoprobes for cellular imaging.Keywords: quantum dots, polymersomes, cellular imaging, cellular uptake

  1. Colloidal Quantum Dot Photovoltaics: A Path Forward

    KAUST Repository

    Kramer, Illan J.

    2011-11-22

    Colloidal quantum dots (CQDs) offer a path toward high-efficiency photovoltaics based on low-cost materials and processes. Spectral tunability via the quantum size effect facilitates absorption of specific wavelengths from across the sun\\'s broad spectrum. CQD materials\\' ease of processing derives from their synthesis, storage, and processing in solution. Rapid advances have brought colloidal quantum dot photovoltaic solar power conversion efficiencies of 6% in the latest reports. These achievements represent important first steps toward commercially compelling performance. Here we review advances in device architecture and materials science. We diagnose the principal phenomenon-electronic states within the CQD film band gap that limit both current and voltage in devices-that must be cured for CQD PV devices to fulfill their promise. We close with a prescription, expressed as bounds on the density and energy of electronic states within the CQD film band gap, that should allow device efficiencies to rise to those required for the future of the solar energy field. © 2011 American Chemical Society.

  2. Cost Effectiveness of DOTS and Non—DOTS Strategies for Smear—Positive Pulmonary Tuberculosis in Beijing

    Institute of Scientific and Technical Information of China (English)

    XU-QUN; JINSHUI-GAO; 等

    2000-01-01

    The cost-effectiveness of DOTS(Directly Observed Treatment,short course)and nonDOTS strategies for smear-positive pulmonary tuberculosis in Beijing was evaluated.Cost calculation was based on the experses of drugs ,chest X-ray films,sputm smears and cultures for the patients.Effectiveness of the intervention was assessed in two aspects:direct benefits to the patients treated and indirect benefits to the others through reduced transmission of tuberculsis;disability adjusted life of year(DALY) was used as an index.The results showed that one DALY could be saved with 45.7 Yuan by DOTS and 471.4 Yuan by non-DOTS.DOTS is a good control strategy for smear-positive tuberculosis.

  3. Cost Effectiveness of DOTS and Non-DOTS Strategies for Smear-positive Pulmonary Tuberculosis in Beijing

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The cost-effectiveness of DOTS (Directly Observed Treatment, short course) and non-DOTS strategies for smear-positive pulmonary tuberculosis in Beijing was evaluated. Cost calculation was based on the expenses of drugs, chest X-ray films, sputum smears and cultures for the patients. Effectiveness of the intervention was assessed in two aspects: direct benefits to the patients treated and indirect benefits to the others through reduced transmission of tuberculosis; disability adjusted life of year (DALY) was used as an index. The results showed that one DALY could be saved with 45.7 Yuan by DOTS and 471.4 Yuan by non-DOTS. DOTS is a good control strategy for smear-positive tuberculosis.

  4. Pulse train amplification and regeneration based on semiconductor quantum dots waveguide

    DEFF Research Database (Denmark)

    Chen, Yaohui; Öhman, Filip; Mørk, Jesper

    2008-01-01

    We numerical analyze pulse train amplification up to 200 Gbit/s in quantum dot amplifiers and present regeneration properties with saturable absorber based on semiconductor quantum dot waveguides.......We numerical analyze pulse train amplification up to 200 Gbit/s in quantum dot amplifiers and present regeneration properties with saturable absorber based on semiconductor quantum dot waveguides....

  5. Ultrashort Dynamics in Quantum Dot Waveguides: Theoretical Analysis and Experimental Investigations

    DEFF Research Database (Denmark)

    Gehrig, E.; Poel, Mike van der; Birkedal, Dan;

    2004-01-01

    Experimental pump-probe measurements and computational modeling on the basis of spatially resolved Quantum Dot Maxwell-Bloch equations allow identification of the processes underlying the ultrafast dot dynamics.......Experimental pump-probe measurements and computational modeling on the basis of spatially resolved Quantum Dot Maxwell-Bloch equations allow identification of the processes underlying the ultrafast dot dynamics....

  6. Electric properties of Ge quantum dot embedded in Si matrix

    Institute of Scientific and Technical Information of China (English)

    MA Xi-ying; SHI Wei-lin

    2005-01-01

    The electric characteristics of Ge quantum dot grown by molecular beam epitaxy in Si matrix were investigated by admittance spectroscopy and deep level transient spectroscopy. The admittance spectroscopy measurements show that the activation energy of 0.341 eV can be considered as the emitting energy of hole from the ground state of the quantum dot. And the capacitance variation with temperature of the sample shows a platform at various frequencies with reverse bias 0.5 V, which indicates that the boundary of space charge region is located at the quantum dot layer where the large confined hole concentration blocks the further extension of space charge region. When the temperature increases from 120 K to 200 K, the holes in the dot emit out completely. The position of the platform shifting with the increase of the applied frequency shows the frequency effects of the charges in the quantum dot. The deep level transient spectroscopy results show that the charge concentration in the Ge quantum dot is a function of the pulse duration and the reverse bias voltage, the activation energy and capture cross-section of hole decrease with the increase of pulse duration due to the Coulomb charging effect. The valence-band offsets of hole in Ge dot obtained by admittance spectroscopy and deep level transient spectroscopy are 0.341 and 0.338 eV, respectively.

  7. Atomically precise, coupled quantum dots fabricated by cleaved edge overgrowth

    Science.gov (United States)

    Wegscheider, W.; Schedelbeck, G.; Bichler, M.; Abstreiter, G.

    Recent progress in the fabrication of quantum dots by molecular beam epitaxy along three directions in space is reviewed. The optical properties of different sample structures consisting of individual quantum dots, pairs of coupled dots as well as of linear arrays of dots are studied by microscopic photoluminescence spectroscopy. The high degree of control over shape, composition and position of the 7×7×7 nm3 size GaAs quantum dots, which form at the intesection of three orthogonal quantum wells, allows a detailed investigation of the influence of coupling between almost identical zero-dimensional objects. In contrast to the inhomogeneously broadened quantum well and quantum wire signals originating from the complex twofold cleaved edge overgrowth structure, the photoluminescence spetrum of an individual quantum dot exhibits a single sharp line (full width at half maximum denomination "artificial atoms" for the quantum dots. It is further demonstrated that an "artifical molecule", characterized by the existence of bonding and antibonding states can be assembled from two of such "artificial atoms". The coupling strength between the "artificial atoms" is adjusted by the "interatomic" distance and is reflected in the energetic separation of the bonding and antibonding levels and the linewidths of the corresponding interband transitions.

  8. InP-quantum dots: Towards high temperature emission

    Energy Technology Data Exchange (ETDEWEB)

    Schulz, Wolfgang-Michael; Rossbach, Robert; Jetter, Michael; Reischle, Matthias; Beirne, Gareth; Michler, Peter [Institut fuer Strahlenphysik, Allmandring 3, 70569 Stuttgart (Germany)

    2007-07-01

    To increase the carrier confinement and luminescence at elevated temperatures for InP-quantum dots, we embedded them in Al{sub 0.50}Ga{sub 0.50}InP. Atomic force microscope measurements are showing a bimodal size distribution of uncapped samples, which can also be seen in the photoluminescence measurements. From time-resolved, power and temperature-dependent PL measurements, we could deduce a confinement energy of 274 meV for small A-type dots and 572 meV for bigger B-type dots. Therefore, the temperature where the thermal reemission of the carriers out of the dots dominates, could be estimated to 160 K for A-type, respectively 250 K for B-type dots. The sample also shows a thermally induced, wetting layer assisted carrier transfer between these bimodal dots, increasing the luminescence intensity of the A-type dots at elevated temperatures. A further increase of the luminescence at elevated temperatures was achieved by placing the QD layer on top of a DBR structure. On account, luminescence up to 460 K was observable. The zero-dimensional behavior was verified with high resolution {mu}-PL and autocorrelation measurements, showing single photon emission at 4 K.

  9. Standardization of the dot enzyme-lynked immunosorbent assay (dot-ELISA for experimental plague

    Directory of Open Access Journals (Sweden)

    Silvia M. L. Montenegro

    1993-03-01

    Full Text Available A dot enzyme linked immunosorbent assay (dot-ELISA was previously developed to detect specific antibodies in rabbits sera immunized against FIA protein obtained from Yersina pestis. This antigen was covalently linked onto the surface of dacron (polyethyleneterephthalate. Here, standard conditions are described for the optimization of this procedure: an amount of 20 ng of FIA protein was fixed onto dacron; anti-rabbit IgG peroxidase conjugate diluted 1:8,000 and 30% non-fat instant milk as blocking substance were used throughout the method. This procedure was compared with that employing nitrocellulose as solid-phase which showed to be more sensitive. However, the method based on dacron did not show false positive reactions against non-immunized rabbits sera at low antigen amount and diluted anti-IgG peroxidase conjugate.

  10. Self-assembled InAs/GaAs quantum dots and quantum dot laser

    Institute of Scientific and Technical Information of China (English)

    王占国; 刘峰奇; 梁基本; 徐波

    2000-01-01

    Systematic study of molecular beam epitaxy-grown self-assembled ln(Ga)As/GaAs, In-AlAs/AlGaAs/GaAs, and InAs/InAIAs/lnP quantum dots (QDs) is demonstrated. By adjusting growth conditions, surprising alignment, preferential elongation, and pronounced sequential coalescence of dots under the specific condition are realized. Room-temperature (RT) continuous-wave (CW) lasing at the wavelength of 960 nm with output power of 1 W is achieved from vertical coupled InAs/GaAs QDs ensemble. The RT threshold current density is 218 A/cm2. An RT CW output power of 0.53 W ensures at least 3 000 h lasing (only drops 0.83 db). This is one of the best results ever reported.

  11. Highly tuneable hole quantum dots in Ge-Si core-shell nanowires

    Science.gov (United States)

    Brauns, Matthias; Ridderbos, Joost; Li, Ang; van der Wiel, Wilfred G.; Bakkers, Erik P. A. M.; Zwanenburg, Floris A.

    2016-10-01

    We define single quantum dots of lengths varying from 60 nm up to nearly half a micron in Ge-Si core-shell nanowires. The charging energies scale inversely with the quantum dot length between 18 and 4 meV. Subsequently, we split up a long dot into a double quantum dot with a separate control over the tunnel couplings and the electrochemical potential of each dot. Both single and double quantum dot configurations prove to be very stable and show excellent control over the electrostatic environment of the dots, making this system a highly versatile platform for spin-based quantum computing.

  12. Lead Chalcogenide Quantum Dots and Quantum Dot Hybrids for Optoelectronic Devices

    OpenAIRE

    Schornbaum, Julia

    2015-01-01

    Semiconductor quantum dots (QDs) exhibit remarkable properties, which include a size-tunable band gap and narrow emission bands. They are also suitable for large-area and low-cost fabrication, due to their solution-processability. Consequently, QDs are very promising for future applications in printable optoelectronic devices. Near-infrared (NIR) active lead chalcogenide QDs hold an enormous potential, as they exhibit optical properties in a wavelength regime, where efficient photoactive mate...

  13. Chemiluminescence behavior of the carbon dots and the reduced state carbon dots

    Energy Technology Data Exchange (ETDEWEB)

    Teng, Ping [Key Laboratory on Luminescence and Real-Time Analysis, Ministry of Education, College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China); Xie, Jianxin [College of Resources and Environment, Yuxi Normal University, Yuxi, Yunnan 653100 (China); Long, Yijuan; Huang, Xiaoxiao; Zhu, Rui; Wang, Xiliang; Liang, Liping [Key Laboratory on Luminescence and Real-Time Analysis, Ministry of Education, College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China); Huang, Yuming, E-mail: ymhuang@swu.edu.cn [Key Laboratory on Luminescence and Real-Time Analysis, Ministry of Education, College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China); Zheng, Huzhi, E-mail: zhenghz@swu.edu.cn [Key Laboratory on Luminescence and Real-Time Analysis, Ministry of Education, College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China)

    2014-02-15

    Potassium permanganate (KMnO{sub 4}) can react with two different carbon nanoparticles, i.e., carbon dots (CDs) and reduced state carbon dots (r-CDs), in a strong acid medium to generate chemiluminescence (CL). Furthermore, the different CL intensities and CL behaviors due to the different surface groups on these two kinds of carbon nanoparticles were confirmed. CL spectra, fluorescence spectra, UV–vis absorption spectra, and electron paramagnanetic resonance spectra were applied to investigate the CL mechanism. The main reaction pathways were proposed as follows: for the CL reaction between CDs and KMnO{sub 4}, the excited states of CDs (CDs{sup ⁎}) and Mn(II) (Mn(II){sup ⁎}) emerged as KMnO{sub 4} could inject holes into CDs, then, the CDs{sup ⁎} and Mn(II){sup ⁎} acted as luminophors to yield CL; in the r-CDs-KMnO{sub 4} system, r-CDs were oxidized by KMnO{sub 4} directly, and CDs{sup ⁎} and Mn(II){sup ⁎} were produced, at the same time, CL occurred. What is more interesting is that the CL intensity of the r-CD system is stronger than that of the CD system, which confirms that functional groups have strong effect on the CL behavior. It inspired us that new carbon nanoparticles with excellent luminous performance can be designed by tuning their surface groups. -- Highlights: • Carbon dots (CDs) and reduced state carbon dots (r-CDs) can react with potassium permanganate (KMnO{sub 4}) in a strong acid to generate chemiluminescence (CL). • With different surface groups, the CL intensity of r-CDs-KMnO{sub 4} system is different from that of CDs-KMnO{sub 4} system. • The CL mechanisms of the two systems were investigated.

  14. Extracting inter-dot tunnel couplings between few donor quantum dots in silicon

    Science.gov (United States)

    Gorman, S. K.; Broome, M. A.; Keizer, J. G.; Watson, T. F.; Hile, S. J.; Baker, W. J.; Simmons, M. Y.

    2016-05-01

    The long term scaling prospects for solid-state quantum computing architectures relies heavily on the ability to simply and reliably measure and control the coherent electron interaction strength, known as the tunnel coupling, t c. Here, we describe a method to extract the t c between two quantum dots (QDs) utilising their different tunnel rates to a reservoir. We demonstrate the technique on a few donor triple QD tunnel coupled to a nearby single-electron transistor (SET) in silicon. The device was patterned using scanning tunneling microscopy-hydrogen lithography allowing for a direct measurement of the tunnel coupling for a given inter-dot distance. We extract {t}{{c}}=5.5+/- 1.8 {{GHz}} and {t}{{c}}=2.2+/- 1.3 {{GHz}} between each of the nearest-neighbour QDs which are separated by 14.5 nm and 14.0 nm, respectively. The technique allows for an accurate measurement of t c for nanoscale devices even when it is smaller than the electron temperature and is an ideal characterisation tool for multi-dot systems with a charge sensor.

  15. Universal parametric correlations of conductance peaks in quantum dots

    International Nuclear Information System (INIS)

    We compute the parametric correlation function of the conductance peaks in chaotic and weakly disordered quantum dots in the Coulomb blockade regime and demonstrate its universality upon an appropriate scaling of the parameter. For a symmetric dot we show that this correlation function is affected by breaking time-reversal symmetry but is independent of the details of the channels in the external leads. We derive a new scaling which depends on the eigenfunctions alone and can be extracted directly from the conductance peak heights. Our results are in excellent agreement with model simulations of a disordered quantum dot. copyright 1996 The American Physical Society

  16. Dielectrophoretic Manipulation and Separation of Microparticles Using Microarray Dot Electrodes

    Directory of Open Access Journals (Sweden)

    Bashar Yafouz

    2014-04-01

    Full Text Available This paper introduces a dielectrophoretic system for the manipulation and separation of microparticles. The system is composed of five layers and utilizes microarray dot electrodes. We validated our system by conducting size-dependent manipulation and separation experiments on 1, 5 and 15 μm polystyrene particles. Our findings confirm the capability of the proposed device to rapidly and efficiently manipulate and separate microparticles of various dimensions, utilizing positive and negative dielectrophoresis (DEP effects. Larger size particles were repelled and concentrated in the center of the dot by negative DEP, while the smaller sizes were attracted and collected by the edge of the dot by positive DEP.

  17. Quantum Dots Microstructured Optical Fiber for X-Ray Detection

    Science.gov (United States)

    DeHaven, Stan; Williams, Phillip; Burke, Eric

    2015-01-01

    Microstructured optical fibers containing quantum dots scintillation material comprised of zinc sulfide nanocrystals doped with magnesium sulfide are presented. These quantum dots are applied inside the microstructured optical fibers using capillary action. The x-ray photon counts of these fibers are compared to the output of a collimated CdTe solid state detector over an energy range from 10 to 40 keV. The results of the fiber light output and associated effects of an acrylate coating and the quantum dot application technique are discussed.

  18. Kondo effect in quantum dots and molecular devices

    Institute of Scientific and Technical Information of China (English)

    JIANG Lang; LI Hongxiang; HU Wenping; ZHU Daoben

    2005-01-01

    Kondo effect is a very important many-body phenomenon in condensed matter physics,which explains why the resistance increases as the temperature is lowered (usually <10 K) in dilute magnetic alloy, and why the conductance increases as temperature is decreased in quantum dots. This paper simply introduces equilibrium and non- equilibrium Kondo effects in quantum dots together with the Kondo effect in quantum dots with even number of electrons (when the singlet and triplet states are degenerate). Furthermore, Kondo effect in single atom/molecular transistors is introduced, which indicates a new way to study Kondo effect.

  19. PL Emission and Shape of Silicon Quantum Dots

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    The calculation results show that the bonding energy and electronic states of silicon quantum dots are different on various curved surfaces, for example, a Si-0-Si bridge bond on curved surface provides the localized levels in band gap and its bonding energy is shallower than that on facet. The red-shifting of PL spectra on smaller silicon quantum dots can be explained by curved surface effect. Experiments demonstrate that silicon quantum dots are activated for emission due to the localized levels provided in curved surface effect.About The Author: Zhong-Mei Huang,Master in Guizhou University.

  20. Thermal Rectification Effect of an Interacting Quantum Dot

    Institute of Scientific and Technical Information of China (English)

    CHEN Xue-Ou; DONG Bing; LEI Xiao-Lin

    2008-01-01

    @@ We investigate the nonlinear thermal transport properties of a single interacting quantum dot with two energy levels tunnel-coupled to two electrodes using nonequilibrium Green function method and Hartree-Fock decoupling approximation. In the case of asymmetric tunnel-couplings to two electrodes, for example, when the upper level of the quantum dot is open for transport, whereas the lower level is blocked, our calculations predict a strong asymmetry for the heat (energy) current, which shows that the quantum dot system may act as a thermal rectifier in this specific situation.

  1. Second Bound State of Biexcitons in Quantum Dots

    Institute of Scientific and Technical Information of China (English)

    XIE Wen-Eang

    2003-01-01

    The second bound state of the biexcitons in a quantum dot, with orbital angular momentum L = 1, is reported. By using the method of few-body physics, the binding energy spectra of the second bound state of a biexciton in a GaAs quantum dot with a parabolic confinement have been calculated as a function of the electron-to-hole mass ratio and the quantum dot size. The fact that the biexcitons have a second bound state may aid in the better understanding of their binding mechanism.

  2. Imaging GABAc Receptors with Ligand-Conjugated Quantum Dots

    Directory of Open Access Journals (Sweden)

    Ian D. Tomlinson

    2007-01-01

    Full Text Available We report a methodology for labeling the GABAc receptor on the surface membrane of intact cells. This work builds upon our earlier work with serotonin-conjugated quantum dots and our studies with PEGylated quantum dots to reduce nonspecific binding. In the current approach, a PEGylated derivative of muscimol was synthesized and attached via an amide linkage to quantum dots coated in an amphiphilic polymer derivative of a modified polyacrylamide. These conjugates were used to image GABAC receptors heterologously expressed in Xenopus laevis oocytes.

  3. Entanglement creation in semiconductor quantum dot charge qubit

    CERN Document Server

    Buscemi, Fabrizio; Bertoni, Andrea

    2010-01-01

    We study theoretically the appearance of quantum correlations in two- and three-electron scattering in single and double dots. The key role played by transport resonances into entanglement formation between the single-particle states is shown. Both reflected and transmitted components of the scattered particle wavefunction are used to evaluate the quantum correlations between the incident carrier and the bound particle(s) in the dots. Our investigation provides a guideline for the analysis of decoherence effects due to the Coulomb scattering in semiconductor quantum dots structures.

  4. Quantum repeaters using orbitals in quantum dot molecules

    Science.gov (United States)

    Ohshima, Toshio

    2016-09-01

    We propose quantum repeaters using quantum dot molecules, in which matter-photon entanglement is generated by Raman scatterings in lambda systems composed of various coherent exciton levels formed in the ensembles of asymmetric coupled quantum dots. In our scheme, the wavelength of Stokes and anti-Stokes photons can be chosen to fulfill the requirements of optical fiber communication. Further, the relative superposition phase in the entangled states can be stabilized by the active feedback to the gate voltage in quantum dot system. These characteristics are favorable for implementing our scheme in practice.

  5. Correlated Coulomb drag in capacitively coupled quantum-dot structures

    DEFF Research Database (Denmark)

    Kaasbjerg, Kristen; Jauho, Antti-Pekka

    2016-01-01

    We study theoretically Coulomb drag in capacitively coupled quantum dots (CQDs) -- a biasdriven dot coupled to an unbiased dot where transport is due to Coulomb mediated energy transfer drag. To this end, we introduce a master-equation approach which accounts for higher-order tunneling (cotunneling....... Interestingly, the direction of the drag current is not determined by the drive current, but by an interplay between the energy-dependent lead couplings. Studying the drag mechanism in a graphene-based CQD heterostructure, we show that the predictions of our theory are consistent with recent experiments...

  6. Optically Modulated Bistability in Quantum Dot Resonant Tunneling Diodes

    Science.gov (United States)

    Weng, Qian-Chun; An, Zheng-Hua; Hou, Ying; Zhu, Zi-Qiang

    2013-04-01

    InAs quantum dots are introduced into resonant tunneling diodes to study the electronic transport behavior, and a wide bistability (ΔV ~ 0.8 V) is observed in the negative differential resistance region. Based on an analytic model, we attribute the observed distinct bistability of a resonant tunneling diodes with quantum dots to the feedback dependence of energy of the electron-storing quantum dots on the tunneling current density. Meanwhile, we find that this wide bistable region can be modulated sensitively by light illumination and becomes narrower with increasing light intensity. Our results suggest that the present devices can be potentially used as sensitive photodetectors in optoelectronic fields.

  7. Electrostatically defined silicon quantum dots with counted antimony donor implants

    Energy Technology Data Exchange (ETDEWEB)

    Singh, M., E-mail: msingh@sandia.gov; Luhman, D. R.; Lilly, M. P. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Center for Integrated Nanotechnologies, Sandia National Laboratories, Albuquerque, New Mexico 87175 (United States); Pacheco, J. L.; Perry, D.; Garratt, E.; Ten Eyck, G.; Bishop, N. C.; Wendt, J. R.; Manginell, R. P.; Dominguez, J.; Pluym, T.; Bielejec, E.; Carroll, M. S. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

    2016-02-08

    Deterministic control over the location and number of donors is crucial to donor spin quantum bits (qubits) in semiconductor based quantum computing. In this work, a focused ion beam is used to implant antimony donors in 100 nm × 150 nm windows straddling quantum dots. Ion detectors are integrated next to the quantum dots to sense the implants. The numbers of donors implanted can be counted to a precision of a single ion. In low-temperature transport measurements, regular Coulomb blockade is observed from the quantum dots. Charge offsets indicative of donor ionization are also observed in devices with counted donor implants.

  8. Realization of electrically tunable single quantum dot nanocavities

    Energy Technology Data Exchange (ETDEWEB)

    Hofbauer, Felix Florian Georg

    2009-03-15

    We investigated the design, fabrication and optical investigation of electrically tunable single quantum dot-photonic crystal defect nanocavities operating in both the weak and strong coupling regimes of the light matter interaction. We demonstrate that the quantum confined Stark effect can be employed to quickly and reversibly switch the dot-cavity coupling, simply by varying a gate voltage. Our results show that exciton transitions from individual dots can be tuned by up to {proportional_to}4 meV relative to the nanocavity mode, before the emission quenches due to carrier tunneling escape from the dots. We directly probe spontaneous emission, irreversible polariton decay and the statistics of the emitted photons from a single-dot nanocavity in the weak and strong coupling regimes. New information is obtained on the nature of the dot-cavity coupling in the weak coupling regime and electrical control of zero dimensional polaritons is demonstrated for the first time. The structures investigated are p-i-n photodiodes consisting of an 180nm thick free-standing GaAs membrane into which a two dimensional photonic crystal is formed by etching a triangular lattice of air holes. Low mode volume nanocavities (V{sub mode}<1.6 ({lambda}/n){sup 3}) are realized by omitting 3 holes in a line to form L3 cavities and a single layer of InGaAs self-assembled quantum dots is embedded into the midpoint of the membrane. The nanocavities are electrically contacted via 35 nm thick p- and n-doped contact layers in the GaAs membrane. In the weak coupling regime, time resolved spectroscopy reveals a {proportional_to}7 x shortening of the spontaneous emission lifetime as the dot is tuned through the nanocavity mode, due to the Purcell effect. Upon strongly detuning the same quantum dot transition from the nanocavity mode we observe an additional {proportional_to}8 x lengthening of the spontaneous emission lifetime. These observations unequivocally highlight two regimes of dot

  9. Electrical control of a single Mn atom in a quantum dot

    OpenAIRE

    Léger, Yoan; Besombes, Lucien; Fernández Rossier, Joaquín; Maingault, Laurent; Mariette, Henri

    2006-01-01

    We report on the reversible electrical control of the magnetic properties of a single Mn atom in an individual quantum dot. Our device permits us to prepare the dot in states with three different electric charges, 0, +1e, and -1e which result in dramatically different spin properties, as revealed by photoluminescence. Whereas in the neutral configuration the quantum dot is paramagnetic, the electron-doped dot spin states are spin rotationally invariant and the hole-doped dot spins states are ...

  10. Charge sensing of a few-donor double quantum dot in silicon

    Energy Technology Data Exchange (ETDEWEB)

    Watson, T. F., E-mail: tfwatson15@gmail.com; Weber, B.; Büch, H.; Fuechsle, M.; Simmons, M. Y., E-mail: michelle.simmons@unsw.edu.au [Australian Research Council Centre of Excellence for Quantum Computation and Communication Technology, University of New South Wales, Sydney, New South Wales 2052 (Australia)

    2015-12-07

    We demonstrate the charge sensing of a few-donor double quantum dot precision placed with atomic resolution scanning tunnelling microscope lithography. We show that a tunnel-coupled single electron transistor (SET) can be used to detect electron transitions on both dots as well as inter-dot transitions. We demonstrate that we can control the tunnel times of the second dot to the SET island by ∼4 orders of magnitude by detuning its energy with respect to the first dot.

  11. Tunneling rate in double quantum dots

    Science.gov (United States)

    Filikhin, Igor; Matinyan, Sergei; Vlahovic, Branislav

    2014-03-01

    We study spectral properties of electron tunneling in double quantum dots (DQDs) (and double quantum wells (DQWs)) and their relation to the geometry. In particular we compare the tunneling in DQW with chaotic and regular geometry, taking into account recent evidence about regularization of the tunneling rate when the QW geometry is chaotic. Our calculations do not support this assumption. We confirm high influence of the QW geometry boundaries on the rate fluctuation along the spectrum. The factors of the effective mass anisotropy and violation of the symmetry of DQD and DQW are also considered. Generally, we found that the small violation of the symmetry drastically affects tunneling. This work is supported by the NSF (HRD-0833184) and NASA (NNX09AV07A).

  12. In Vivo Imaging of Quantum Dots

    Science.gov (United States)

    Texier, Isabelle; Josser, Véronique

    Noninvasive whole-body near-infrared fluorescence imaging is now acknowledged as a powerful method for the molecular mapping of biological events in live small animals such as mouse models. With outstanding optical properties such as high fluorescence quantum yields and low photobleaching rates, quantum dots (QDs) are labels of choice in the near-infrared domain. The main applications described in the literature for in vivo imaging of mice after injection of QDs encompass imaging of lymph nodes and tumors and cell tracking. Standard methods for the preparation, the purification, and the in vivo fluorescence whole-body imaging of QDs in the live mouse are described. Nanoparticles coated by PEG chains of different sizes and terminal groups are prepared using 705-nm-emitting commercial QDs. Their biodistribution after intravenous or intradermal injections in tumor-bearing mice is reported here.

  13. Mitochondria as target of Quantum dots toxicity

    International Nuclear Information System (INIS)

    Highlights: → The present work investigated the toxicity of CdTe QDs on the function of mitochondria isolated from rat livers. → These results will help us learn more about QDs toxicity at subcellular (mitochondrial) level. → QDs toxicity on mitochondria indicates that the QDs require to be further improved before they can be safely used in clinic. - Abstract: Quantum dots (QDs) hold great promise in many biological applications, with the persistence of safety concerns about the environment and human health. The present work investigated the potential toxicity of CdTe QDs on the function of mitochondria isolated from rat livers by examining mitochondrial respiration, swelling, and lipid peroxidation. We observed that QDs can significantly affect the mitochondrial membrane properties, bioenergetics and induce mitochondrial permeability transition (MPT). These results will help us learn more about QDs toxicity at subcellular (mitochondrial) level.

  14. Selective area epitaxy of quantum dots

    International Nuclear Information System (INIS)

    Full text: We investigate selective-area-epitaxy (SAE) as a tool for selectively controlling the physical and optical properties of quantum-dots (QDs), aiming at integration of QD devices. MOCVD growth of InGaAs/lnAs QDs on GaAs wafers patterned with pairs of SiO2 stripes is studied. Atomic force microscopy and cathodoluminescence are used for characterisation of these QDs. We show that InGaAs QD luminescence can be tuned over a range of 100nm by varying the dimensions of and/or spacings between the SiO2 stripes. Growth of InGaAs quantum-well and QDs on different parts of the same wafer, without using etch and regrowth techniques is also demonstrated. Results for the InAs/GaAs system are also presented. Copyright (2005) Australian Institute of Physics

  15. Building devices from colloidal quantum dots.

    Science.gov (United States)

    Kagan, Cherie R; Lifshitz, Efrat; Sargent, Edward H; Talapin, Dmitri V

    2016-08-26

    The continued growth of mobile and interactive computing requires devices manufactured with low-cost processes, compatible with large-area and flexible form factors, and with additional functionality. We review recent advances in the design of electronic and optoelectronic devices that use colloidal semiconductor quantum dots (QDs). The properties of materials assembled of QDs may be tailored not only by the atomic composition but also by the size, shape, and surface functionalization of the individual QDs and by the communication among these QDs. The chemical and physical properties of QD surfaces and the interfaces in QD devices are of particular importance, and these enable the solution-based fabrication of low-cost, large-area, flexible, and functional devices. We discuss challenges that must be addressed in the move to solution-processed functional optoelectronic nanomaterials. PMID:27563099

  16. Wet electron microscopy with quantum dots.

    Science.gov (United States)

    Timp, Winston; Watson, Nicki; Sabban, Alon; Zik, Ory; Matsudaira, Paul

    2006-09-01

    Wet electron microscopy (EM) is a new imaging method with the potential to allow higher spatial resolution of samples. In contrast to most EM methods, it requires little time to perform and does not require complicated equipment or difficult steps. We used this method on a common murine macrophage cell line, IC-21, in combination with various stains and preparations, to collect high resolution images of the actin cytoskeleton. Most importantly, we demonstrated the use of quantum dots in conjunction with this technique to perform light/electron correlation microscopy. We found that wet EM is a useful tool that fits into a niche between the simplicity of light microscopy and the high spatial resolution of EM.

  17. Biosensing with Luminescent Semiconductor Quantum Dots

    Directory of Open Access Journals (Sweden)

    Hedi Mattoussi

    2006-08-01

    Full Text Available Luminescent semiconductor nanocrystals or quantum dots (QDs are a recentlydeveloped class of nanomaterial whose unique photophysical properties are helping tocreate a new generation of robust fluorescent biosensors. QD properties of interest forbiosensing include high quantum yields, broad absorption spectra coupled to narrow sizetunablephotoluminescent emissions and exceptional resistance to both photobleaching andchemical degradation. In this review, we examine the progress in adapting QDs for severalpredominantly in vitro biosensing applications including use in immunoassays, asgeneralized probes, in nucleic acid detection and fluorescence resonance energy transfer(FRET - based sensing. We also describe several important considerations when workingwith QDs mainly centered on the choice of material(s and appropriate strategies forattaching biomolecules to the QDs.

  18. Universal Braess paradox in open quantum dots

    Science.gov (United States)

    Barbosa, A. L. R.; Bazeia, D.; Ramos, J. G. G. S.

    2014-10-01

    We present analytical and numerical results that demonstrate the presence of the Braess paradox in chaotic quantum dots. The paradox that we identify, originally perceived in classical networks, shows that the addition of more capacity to the network can suppress the current flow in the universal regime. We investigate the weak localization term, showing that it presents the paradox encoded in a saturation minimum of the conductance, under the presence of hyperflow in the external leads. In addition, we demonstrate that the weak localization suffers a transition signal depending on the overcapacity lead and presents an echo on the magnetic crossover before going to zero due to the full time-reversal symmetry breaking. We also show that the quantum interference contribution can dominate the Ohm term in the presence of constrictions and that the corresponding Fano factor engenders an anomalous behavior.

  19. Quantum dots for next-generation photovoltaics

    Directory of Open Access Journals (Sweden)

    Octavi E. Semonin

    2012-11-01

    Full Text Available Colloidal quantum-confined semiconductor nanostructures are an emerging class of functional material that are being developed for novel solar energy conversion strategies. One of the largest losses in a bulk or thin film solar cell occurs within a few picoseconds after the photon is absorbed, as photons with energy larger than the semiconductor bandgap produce charge-carriers with excess kinetic energy, which is then dissipated via phonon emission. Semiconductor nanostructures, where at least one dimension is small enough to produce quantum confinement effects, provide new pathways for controlling energy flow and therefore have the potential to increase the efficiency of the primary photoconversion step. In this review, we provide the current status of research efforts towards utilizing the unique properties of colloidal quantum dots (nanocrystals confined in three dimensions in prototype solar cells and demonstrate that these unique systems have the potential to bypass the Shockley-Queisser single-junction limit for solar photon conversion.

  20. Protease-activated quantum dot probes

    International Nuclear Information System (INIS)

    We have developed a novel nanoparticulate luminescent probe with inherent signal amplification upon interaction with a targeted proteolytic enzyme. This construct may be useful for imaging in cancer detection and diagnosis. In this system, quantum dots (QDs) are bound to gold nanoparticles (AuNPs) via a proteolytically degradable peptide sequence to non-radiatively suppress luminescence. A 71% reduction in luminescence was achieved with conjugation of AuNPs to QDs. Release of AuNPs by peptide cleavage restores radiative QD photoluminescence. Initial studies observed a 52% rise in luminescence over 47 h of exposure to 0.2 mg/mL collagenase. These probes can be customized for targeted degradation simply by changing the sequence of the peptide linker

  1. Semiconductor Quantum Dots for Biomedicial Applications

    Directory of Open Access Journals (Sweden)

    Lijia Shao

    2011-12-01

    Full Text Available Semiconductor quantum dots (QDs are nanometre-scale crystals, which have unique photophysical properties, such as size-dependent optical properties, high fluorescence quantum yields, and excellent stability against photobleaching. These properties enable QDs as the promising optical labels for the biological applications, such as multiplexed analysis of immunocomplexes or DNA hybridization processes, cell sorting and tracing, in vivo imaging and diagnostics in biomedicine. Meanwhile, QDs can be used as labels for the electrochemical detection of DNA or proteins. This article reviews the synthesis and toxicity of QDs and their optical and electrochemical bioanalytical applications. Especially the application of QDs in biomedicine such as delivering, cell targeting and imaging for cancer research, and in vivo photodynamic therapy (PDT of cancer are briefly discussed.

  2. Mitochondria as target of Quantum dots toxicity

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jiahan; Zhang, Yue; Xiao, Qi; Tian, Fangfang; Liu, Xiaorong; Li, Ran; Zhao, Guangyuan; Jiang, Fenglei [State Key Laboratory of Virology and Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072 (China); Liu, Yi, E-mail: yiliuchem@whu.edu.cn [State Key Laboratory of Virology and Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072 (China)

    2011-10-30

    Highlights: {yields} The present work investigated the toxicity of CdTe QDs on the function of mitochondria isolated from rat livers. {yields} These results will help us learn more about QDs toxicity at subcellular (mitochondrial) level. {yields} QDs toxicity on mitochondria indicates that the QDs require to be further improved before they can be safely used in clinic. - Abstract: Quantum dots (QDs) hold great promise in many biological applications, with the persistence of safety concerns about the environment and human health. The present work investigated the potential toxicity of CdTe QDs on the function of mitochondria isolated from rat livers by examining mitochondrial respiration, swelling, and lipid peroxidation. We observed that QDs can significantly affect the mitochondrial membrane properties, bioenergetics and induce mitochondrial permeability transition (MPT). These results will help us learn more about QDs toxicity at subcellular (mitochondrial) level.

  3. Preparation and Application of Fluorescent Carbon Dots

    Directory of Open Access Journals (Sweden)

    Jun Zuo

    2015-01-01

    Full Text Available Fluorescent carbon dots (CDs are a novel type of fluorescent nanomaterials, which not only possess the specific quantum confinement effects of nanomaterials due to the small size of nanomaterials, but also have good biocompatibility and high fluorescence. Meanwhile, fluorescence CDs overcome the shortcomings of high toxicity of traditional nanomaterials. Moreover, the preparation procedure of fluorescent CDs is simple and easy. Therefore, fluorescent CDs have great potential applied in photocatalysis, biochemical sensing, bioimaging, drug delivery, and other related areas. In this paper, recent hot researches on fluorescent CDs are reviewed and some problems in the progress of fluorescent CDs are also summarized. At last, a future outlook in this direction is presented.

  4. Universal Braess paradox in open quantum dots.

    Science.gov (United States)

    Barbosa, A L R; Bazeia, D; Ramos, J G G S

    2014-10-01

    We present analytical and numerical results that demonstrate the presence of the Braess paradox in chaotic quantum dots. The paradox that we identify, originally perceived in classical networks, shows that the addition of more capacity to the network can suppress the current flow in the universal regime. We investigate the weak localization term, showing that it presents the paradox encoded in a saturation minimum of the conductance, under the presence of hyperflow in the external leads. In addition, we demonstrate that the weak localization suffers a transition signal depending on the overcapacity lead and presents an echo on the magnetic crossover before going to zero due to the full time-reversal symmetry breaking. We also show that the quantum interference contribution can dominate the Ohm term in the presence of constrictions and that the corresponding Fano factor engenders an anomalous behavior. PMID:25375575

  5. Effect of Intra-Dot Coulomb Interaction on Andreev Reflection in Normal-Metal/Quantum-Dot/Superconductor System

    Institute of Scientific and Technical Information of China (English)

    ZHU Yu; SUN Qing-Feng; LIN Tsung-Han

    2001-01-01

    We investigate the effect of intra-dot Coulomb interaction on the Andreev reflection in a normalmetal/quantum-dot/superconductor (N-QD-S) system with multiple levels in the quantum dot, in the regime where the intra-dot interacting constant is comparable to the energy gap of superconducting lead. By using nonequilibrium Green function method, the averaged occupation of electrons in the quantum dot and the Andreev reflection (AR) current are studied. Comparing to the case of non-interacting quantum dot, the system shows significant changes for the a two-step-like behavior; and the I-Vg shows two groups of peaks, separated by U and with equal heights, where Vg is the gate voltage and U denotes the intra-dot Coulomb interaction constant. (ii) For finite bias voltage, dips, superposed V ≥ U/2, extra AR current peaks occur between the two groups of the peaks. Besides, the properties of the heights of the AR current peaks are more complicated.``

  6. PREFACE: Quantum dots as probes in biology

    Science.gov (United States)

    Cieplak, Marek

    2013-05-01

    The recent availability of nanostructured materials has resulted in an explosion of research focused on their unique optical, thermal, mechanical and magnetic properties. Optical imagining, magnetic enhancement of contrast and drug delivery capabilities make the nanoparticles of special interest in biomedical applications. These materials have been involved in the development of theranostics—a new field of medicine that is focused on personalized tests and treatment. It is likely that multimodal nanomaterials will be responsible for future diagnostic advances in medicine. Quantum dots (QD) are nanoparticles which exhibit luminescence either through the formation of three-dimensional excitons or excitations of the impurities. The excitonic luminescence can be tuned by changing the size (the smaller the size, the higher the frequency). QDs are usually made of semiconducting materials. Unlike fluorescent proteins and organic dyes, QDs resist photobleaching, allow for multi-wavelength excitations and have narrow emission spectra. The techniques to make QDs are cheap and surface modifications and functionalizations can be implemented. Importantly, QDs could be synthesized to exhibit useful optomagnetic properties and, upon functionalization with an appropriate biomolecule, directed towards a pre-selected target for diagnostic imaging and photodynamic therapy. This special issue on Quantum dots in Biology is focused on recent research in this area. It starts with a topical review by Sreenivasan et al on various physical mechanisms that lead to the QD luminescence and on using wavelength shifts for an improvement in imaging. The next paper by Szczepaniak et al discusses nanohybrids involving QDs made of CdSe coated by ZnS and combined covalently with a photosynthetic enzyme. These nanohybrids are shown to maintain the enzymatic activity, however the enzyme properties depend on the size of a QD. They are proposed as tools to study photosynthesis in isolated

  7. Advanced Epitaxial Lift-Off Quantum Dot Photovoltaic Devices Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to develop a high-efficiency, triple-junction, epitaxial lift-off (ELO) solar cell by incorporating quantum dots (QDs) within the current-limiting...

  8. Type 2 quantum dots in Ge/Si system

    CERN Document Server

    Dvurechenskij, A V

    2001-01-01

    The results on the electronic structure of spatially indirect excitons, multiparticle excitonic complexes, and negative interband photoconductivity in arrays of Ge/Si type 2 quantum dots are presented. These data have been compared with the well known results for type 2 A sup I sup I sup I B sup V and A sup I sup I B sup V sup I -based heterostructures with quantum dots. Fundamental physical phenomena are found to be the result of an increase in the binding energy of excitons in quantum dots as compared with that of free excitons in bulk homogeneous materials; the shortwave shift of exciton transition energy at multiparticle complexes production (charges excitons, biexcitons), as well as the trapping of equilibrium carrier by localized states induced by the charged quantum dot electric field

  9. Kondo effect for electron transport through an artificial quantum dot

    Institute of Scientific and Technical Information of China (English)

    Sun Ke-Wei; Xiong Shi-Jie

    2006-01-01

    We have calculated the transport properties of electron through an artificial quantum dot by using the numerical renormalization group technique in this paper.We obtain the conductance for the system of a quantum dot which is embedded in a one-dimensional chain in zero and finite temperature cases.The external magnetic field gives rise to a negative magnetoconductance in the zero temperature case.It increases as the external magnetic field increases.We obtain the relation between the coupling coefficient and conductance.If the interaction is big enough to prevent conduction electrons from tunnelling through the dot,the dispersion effect is dominant in this case.In the Kondo temperature regime,we obtain the conductivity of a quantum dot system with Kondo correlation.

  10. Quantum Dots: An Experiment for Physical or Materials Chemistry

    Science.gov (United States)

    Winkler, L. D.; Arceo, J. F.; Hughes, W. C.; DeGraff, B. A.; Augustine, B. H.

    2005-01-01

    An experiment is conducted for obtaining quantum dots for physical or materials chemistry. This experiment serves to both reinforce the basic concept of quantum confinement and providing a useful bridge between the molecular and solid-state world.

  11. Fabrication of quantum-dot devices in graphene

    Directory of Open Access Journals (Sweden)

    Satoshi Moriyama, Yoshifumi Morita, Eiichiro Watanabe, Daiju Tsuya, Shinya Uji, Maki Shimizu and Koji Ishibashi

    2010-01-01

    Full Text Available We describe our recent experimental results on the fabrication of quantum-dot devices in a graphene-based two-dimensional system. Graphene samples were prepared by micromechanical cleavage of graphite crystals on a SiO2/Si substrate. We performed micro-Raman spectroscopy measurements to determine the number of layers of graphene flakes during the device fabrication process. By applying a nanofabrication process to the identified graphene flakes, we prepared a double-quantum-dot device structure comprising two lateral quantum dots coupled in series. Measurements of low-temperature electrical transport show the device to be a series-coupled double-dot system with varied interdot tunnel coupling, the strength of which changes continuously and non-monotonically as a function of gate voltage.

  12. Carbon Dot Based Sensing of Dopamine and Ascorbic Acid

    Directory of Open Access Journals (Sweden)

    Upama Baruah

    2014-01-01

    Full Text Available We demonstrate carbon dot based sensor of catecholamine, namely, dopamine and ascorbic acid. Carbon dots (CDs were prepared from a green source: commercially available Assam tea. The carbon dots prepared from tea had particle sizes of ∼0.8 nm and are fluorescent. Fluorescence of the carbon dots was found to be quenched in the presence of dopamine and ascorbic acid with greater sensitivity for dopamine. The minimum detectable limits were determined to be 33 μM and 98 μM for dopamine and ascorbic acid, respectively. The quenching constants determined from Stern-Volmer plot were determined to be 5 × 10−4 and 1 × 10−4 for dopamine and ascorbic acid, respectively. A probable mechanism of quenching has been discussed in the paper.

  13. A triple quantum dot based nano-electromechanical memory device

    International Nuclear Information System (INIS)

    Colloidal quantum dots (CQDs) are free-standing nano-structures with chemically tunable electronic properties. This tunability offers intriguing possibilities for nano-electromechanical devices. In this work, we consider a nano-electromechanical nonvolatile memory (NVM) device incorporating a triple quantum dot (TQD) cluster. The device operation is based on a bias induced motion of a floating quantum dot (FQD) located between two bound quantum dots (BQDs). The mechanical motion is used for switching between two stable states, “ON” and “OFF” states, where ligand-mediated effective interdot forces between the BQDs and the FQD serve to hold the FQD in each stable position under zero bias. Considering realistic microscopic parameters, our quantum-classical theoretical treatment of the TQD reveals the characteristics of the NVM

  14. Charge-extraction strategies for colloidal quantum dot photovoltaics

    KAUST Repository

    Lan, Xinzheng

    2014-02-20

    The solar-power conversion efficiencies of colloidal quantum dot solar cells have advanced from sub-1% reported in 2005 to a record value of 8.5% in 2013. Much focus has deservedly been placed on densifying, passivating and crosslinking the colloidal quantum dot solid. Here we review progress in improving charge extraction, achieved by engineering the composition and structure of the electrode materials that contact the colloidal quantum dot film. New classes of structured electrodes have been developed and integrated to form bulk heterojunction devices that enhance photocharge extraction. Control over band offsets, doping and interfacial trap state densities have been essential for achieving improved electrical communication with colloidal quantum dot solids. Quantum junction devices that not only tune the optical absorption spectrum, but also provide inherently matched bands across the interface between p-and n-materials, have proven that charge separation can occur efficiently across an all-quantum-tuned rectifying junction. © 2014 Macmillan Publishers Limited.

  15. Quantum dot conjugates in a sub-micrometer fluidic channel

    Science.gov (United States)

    Stavis, Samuel M.; Edel, Joshua B.; Samiee, Kevan T.; Craighead, Harold G.

    2010-04-13

    A nanofluidic channel fabricated in fused silica with an approximately 500 nm square cross section was used to isolate, detect and identify individual quantum dot conjugates. The channel enables the rapid detection of every fluorescent entity in solution. A laser of selected wavelength was used to excite multiple species of quantum dots and organic molecules, and the emission spectra were resolved without significant signal rejection. Quantum dots were then conjugated with organic molecules and detected to demonstrate efficient multicolor detection. PCH was used to analyze coincident detection and to characterize the degree of binding. The use of a small fluidic channel to detect quantum dots as fluorescent labels was shown to be an efficient technique for multiplexed single molecule studies. Detection of single molecule binding events has a variety of applications including high throughput immunoassays.

  16. Dot-Projection Photogrammetry and Videogrammetry of Gossamer Space Structures

    Science.gov (United States)

    Pappa, Richard S.; Black, Jonathan T.; Blandino, Joseph R.; Jones, Thomas W.; Danehy, Paul M.; Dorrington, Adrian A.

    2003-01-01

    This paper documents the technique of using hundreds or thousands of projected dots of light as targets for photogrammetry and videogrammetry of gossamer space structures. Photogrammetry calculates the three-dimensional coordinates of each target on the structure, and videogrammetry tracks the coordinates versus time. Gossamer structures characteristically contain large areas of delicate, thin-film membranes. Examples include solar sails, large antennas, inflatable solar arrays, solar power concentrators and transmitters, sun shields, and planetary balloons and habitats. Using projected-dot targets avoids the unwanted mass, stiffness, and installation costs of traditional retroreflective adhesive targets. Four laboratory applications are covered that demonstrate the practical effectiveness of white-light dot projection for both static-shape and dynamic measurement of reflective and diffuse surfaces, respectively. Comparisons are made between dot-projection videogrammetry and traditional laser vibrometry for membrane vibration measurements. The paper closes by introducing a promising extension of existing techniques using a novel laser-induced fluorescence approach.

  17. Optically induced magnetization in diluted magnetic quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    John Peter, A. [Government Arts College, Melur 625 106, Madurai (India)], E-mail: a_johnpeter@rediffmail.com; Lily Mary Eucharista, K. [Arul Anandar College, Karumathur 625 514, Madurai (India)

    2009-03-15

    We report the effect of intense laser field on donor impurities in a semimagnetic Cd{sub 1-x{sub in}}Mn{sub x{sub in}}Te/Cd{sub 1-x{sub out}}Mn{sub x{sub out}}Te quantum dot. The spin polaronic energy of different Mn{sup 2+} is evaluated for different dot radii using a mean field theory in the presence of laser field. Magnetization is calculated for various concentrations of Mn{sup 2+} ions with different dot sizes. Significant magnetization of Mn spins can be obtained through the formation of polarized exciton magnetic polarons (EMPs). A rapid decrease of the laser dressed donor ionization energy for different values of dot sizes with increasing field intensity is predicted. Also, it is found that the polarization of EMPs increases rapidly at higher excitation energies.

  18. Hydrogenic Donor in a Spherical Quantum Dot with Different Confinements

    Institute of Scientific and Technical Information of China (English)

    A. John Peter; K. Navaneethakrishnan

    2009-01-01

    Binding energies of a hydrogenic donor in a spherical GaAs quantum dot surrounded by Ga1-xAlxAs matrix are calculated. The results are presented for realistic barrier heights corresponding to different values of x (x < 0.4). The calculations are performed under two different conditions: (i) a spherical dot with square well confinement and (ii) a dot with parabolic potential well confinement. The results show that (i) the donor ionization energies are always higher under parabolic confinement as compared to a dot of the same radius under square well confinement and (ii) the oscillator strengths coupling ground state with excited states are two orders larger under parabolic confinement. Our results are in agreement with the results of other researchers.

  19. Using a quantum dot system to realize perfect state transfer

    Institute of Scientific and Technical Information of China (English)

    Li Ji; Wu Shi-Hai; Zhang Wen-Wen; Xi Xiao-Qiang

    2011-01-01

    There are some disadvantages to Nikolopoulos et al.'s protocol [Nikolopoulos G M,Petrosyan D and Lambropoulos P 2004 Europhys.Lett.65 297] where a quantum dot system is used to realize quantum communication.To overcome these disadvantages,we propose a protocol that uses a quantum dot array to construct a four-qubit spin chain to realize perfect quantum state transfer (PQST).First,we calculate the interaction relation for PQST in the spin chain.Second,we review the interaction between the quantum dots in the Heitler-London approach.Third,we present a detailed program for designing the proper parameters of a quantum dot array to realize PQST.

  20. Non-Markovian spontaneous emission from a single quantum dot

    DEFF Research Database (Denmark)

    Madsen, Kristian Høeg; Ates, Serkan; Lund-Hansen, Toke;

    2011-01-01

    We observe non-Markovian dynamics of a single quantum dot when tuned into resonance with a cavity mode. Excellent agreement between experiment and theory is observed providing the first quantitative description of such a system....

  1. [Louis Braille (1809-1852)--inventor of raised dots system].

    Science.gov (United States)

    Maciejewicz, Piotr; Kopacz, Dorota

    2005-01-01

    Louis Braille was born on January 4th 1809 in Coupvray, France. An injury to his eye at the age of three, resulted in total loss of vision. In 1819 he entered the Institute for Blind Youth in Paris. There he would live, study, and later teach. When he was fifteen, he developed system of reading and writing by means of raised dots, which is known today as Braille. The basis of the Braille system is known as a Braille cell. The cell is comprised of six dots numbered in a specific order. Each dot or combination of dots represents a letter of the alphabet. This Braille system has established itself internationally and formed the basic Braille for all languages.

  2. A fast "hybrid" silicon double quantum dot qubit

    CERN Document Server

    Shi, Zhan; Prance, J R; Gamble, John King; Koh, Teck Seng; Shim, Yun-Pil; Hu, Xuedong; Savage, D E; Lagally, M G; Eriksson, M A; Friesen, Mark; Coppersmith, S N

    2011-01-01

    We propose a quantum dot qubit architecture that has an attractive combination of speed and fabrication simplicity. It consists of a double quantum dot with one electron in one dot and two electrons in the other. The qubit itself is a set of two states with total spin quantum numbers $S^2=3/4$ ($S=\\half$) and $S_z = -\\half$, with the two different states being singlet and triplet in the doubly occupied dot. The architecture is relatively simple to fabricate, a universal set of fast operations can be implemented electrically, and the system has potentially long decoherence times. These are all extremely attractive properties for use in quantum information processing devices.

  3. A Novel Particle Detector: Quantum Dot Doped Liquid Scintillator

    Science.gov (United States)

    Winslow, Lindley; Conrad, Janet; Jerry, Ruel

    2010-02-01

    Quantum dots are semiconducting nanocrystals. When excited by light shorter then their characteristic wavelength, they re-emit in a narrow band around this wavelength. The size of the quantum is proportional to the characteristic wavelength so they can be tuned for many applications. CdS quantum dots are made in wavelengths from 360nm to 460nm, a perfect range for the sensitivity of photo-multiplier tubes. The synthesis of quantum dots automatically leaves them in toluene, a good organic scintillator and Cd is a particularly interesting material as it has one of the highest thermal neutron cross sections and has several neutrinoless double beta decay and double electron capture isotopes. The performance of quantum dot loaded scintillator compared to standard scintillators is measured and some unique properties presented. )

  4. The transfer matrix approach to circular graphene quantum dots

    Science.gov (United States)

    Chau Nguyen, H.; Nguyen, Nhung T. T.; Nguyen, V. Lien

    2016-07-01

    We adapt the transfer matrix (T-matrix) method originally designed for one-dimensional quantum mechanical problems to solve the circularly symmetric two-dimensional problem of graphene quantum dots. Similar to one-dimensional problems, we show that the generalized T-matrix contains rich information about the physical properties of these quantum dots. In particular, it is shown that the spectral equations for bound states as well as quasi-bound states of a circular graphene quantum dot and related quantities such as the local density of states and the scattering coefficients are all expressed exactly in terms of the T-matrix for the radial confinement potential. As an example, we use the developed formalism to analyse physical aspects of a graphene quantum dot induced by a trapezoidal radial potential. Among the obtained results, it is in particular suggested that the thermal fluctuations and electrostatic disorders may appear as an obstacle to controlling the valley polarization of Dirac electrons.

  5. Energy levels of hybrid monolayer-bilayer graphene quantum dots

    Science.gov (United States)

    Mirzakhani, M.; Zarenia, M.; Ketabi, S. A.; da Costa, D. R.; Peeters, F. M.

    2016-04-01

    Often real samples of graphene consist of islands of both monolayer and bilayer graphene. Bound states in such hybrid quantum dots are investigated for (i) a circular single-layer graphene quantum dot surrounded by an infinite bilayer graphene sheet and (ii) a circular bilayer graphene quantum dot surrounded by an infinite single-layer graphene. Using the continuum model and applying zigzag boundary conditions at the single-layer-bilayer graphene interface, we obtain analytical results for the energy levels and the corresponding wave spinors. Their dependence on perpendicular magnetic and electric fields are studied for both types of quantum dots. The energy levels exhibit characteristics of interface states, and we find anticrossings and closing of the energy gap in the presence of a bias potential.

  6. Electro-absorption of silicene and bilayer graphene quantum dots

    Science.gov (United States)

    Abdelsalam, Hazem; Talaat, Mohamed H.; Lukyanchuk, Igor; Portnoi, M. E.; Saroka, V. A.

    2016-07-01

    We study numerically the optical properties of low-buckled silicene and AB-stacked bilayer graphene quantum dots subjected to an external electric field, which is normal to their surface. Within the tight-binding model, the optical absorption is calculated for quantum dots, of triangular and hexagonal shapes, with zigzag and armchair edge terminations. We show that in triangular silicene clusters with zigzag edges a rich and widely tunable infrared absorption peak structure originates from transitions involving zero energy states. The edge of absorption in silicene quantum dots undergoes red shift in the external electric field for triangular clusters, whereas blue shift takes place for hexagonal ones. In small clusters of bilayer graphene with zigzag edges the edge of absorption undergoes blue/red shift for triangular/hexagonal geometry. In armchair clusters of silicene blue shift of the absorption edge takes place for both cluster shapes, while red shift is inherent for both shapes of the bilayer graphene quantum dots.

  7. Intraband Relaxation and Its Influences on Quantum Dot Lasers

    Institute of Scientific and Technical Information of China (English)

    DENG Sheng-Ling; HUANG Yong-Zhen; YU Li-Juan

    2005-01-01

    @@ A comprehensive two-level numerical model is developed to describe carrier distribution in a quantum-dot laser. Light-emission spectra with different intraband relaxation rates (2ps, 7.5ps and 20ps) are calculated and analysed to investigate the influence of relaxation rates on performance of the quantum-dot laser. The results indicate that fast intraband relaxation favours not only the ground state single mode operation but also the higher injection efficiency.

  8. Dephasing of quantum dot exciton polaritons in electrically tunable nanocavities

    OpenAIRE

    Laucht, A.; Hauke, N.; Villas-Bôas, J. M.; Hofbauer, F.; Kaniber, M.; Böhm, G.; Finley, J.J.

    2009-01-01

    We experimentally and theoretically investigate dephasing of zero dimensional microcavity polaritons in electrically tunable single dot photonic crystal nanocavities. Such devices allow us to alter the dot-cavity detuning in-situ and to directly probe the influence on the emission spectrum of varying the incoherent excitation level and the lattice temperature. By comparing our results with theory we obtain the polariton dephasing rate and clarify its dependence on optical excitation power and...

  9. THz Electro-absorption Effect in Quantum Dots

    DEFF Research Database (Denmark)

    Turchinovich, Dmitry; Monozon, Boris S.; Livshits, Daniil A.;

    2011-01-01

    Instantaneous electro-absorption effect in quantum dots, induced by electric field of THz pulse with 3 THz bandwidth is demonstrated in THz pump - optical probe experiment. This effect may be promising for Tbit/s wireless transmission systems.......Instantaneous electro-absorption effect in quantum dots, induced by electric field of THz pulse with 3 THz bandwidth is demonstrated in THz pump - optical probe experiment. This effect may be promising for Tbit/s wireless transmission systems....

  10. Quantum Optics with Quantum Dots in Photonic Nanowires

    DEFF Research Database (Denmark)

    Gérard, J.-M.; Claudon, J.; Bleuse, J.;

    2011-01-01

    We review recent studies performed on InAs quantum dots embedded in GaAs photonic wires, which highlight the strong interest of the photonic wire geometry for quantum optics experiments and quantum optoelectronic devices.......We review recent studies performed on InAs quantum dots embedded in GaAs photonic wires, which highlight the strong interest of the photonic wire geometry for quantum optics experiments and quantum optoelectronic devices....

  11. Highly Efficient Spontaneous Emission from Self-Assembled Quantum Dots

    DEFF Research Database (Denmark)

    Johansen, Jeppe; Lund-Hansen, Toke; Hvam, Jørn Märcher;

    2006-01-01

    We present time resolved measurements of spontaneous emission (SE) from InAs/GaAs quantum dots (QDs). The measurements are interpreted using Fermi's Golden Rule and from this analysis we establish the parameters for high quantum efficiency.......We present time resolved measurements of spontaneous emission (SE) from InAs/GaAs quantum dots (QDs). The measurements are interpreted using Fermi's Golden Rule and from this analysis we establish the parameters for high quantum efficiency....

  12. Solution-processed nanocrystal quantum dot tandem solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Joshua J.; Lim, Yee-Fun [School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853 (United States); Wenger, Whitney N.; Hoffman, Rachel S.; Hanrath, Tobias [School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY 14853 (United States); Luria, Justin; Marohn, John A. [Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853 (United States); Jasieniak, Jacek [CSIRO Materials Science and Engineering, Bayview Ave, Clayton, Victoria 3168 (Australia)

    2011-07-26

    Solution-processed tandem solar cells created from nanocrystal quantum dots with size-tuned energy levels are demonstrated. Prototype devices featuring interconnected quantum dot layers of cascaded energy gaps exhibit IR sensitivity and an open circuit voltage, V{sub oc}, approaching 1 V. The tandem solar cell performance depends critically on the optical and electrical properties of the interlayer. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Spin and edge channel dependent transport through quantum dots

    International Nuclear Information System (INIS)

    We investigate the influence of spin polarized currents and non-equilibrated edge channels on the transport properties of a single quantum dot. Polarized currents are realized by the manual depletion of edge channels in high magnetic fields via a metallic top gate covering the source contact in the system. We observe a suppression and enhancement in the conductance of the quantum dot dependent on the edge channel configuration in the leads.

  14. Spin and edge channel dependent transport through quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Ridder, T; Rogge, M C; Haug, R J [Institut fuer Festkoerperphysik, Gottfried Wilhelm Leibniz Universitaet Hannover, Appelstrasse 2, D-30167 Hannover (Germany)], E-mail: ridder@nano.uni-hannover.de

    2008-11-12

    We investigate the influence of spin polarized currents and non-equilibrated edge channels on the transport properties of a single quantum dot. Polarized currents are realized by the manual depletion of edge channels in high magnetic fields via a metallic top gate covering the source contact in the system. We observe a suppression and enhancement in the conductance of the quantum dot dependent on the edge channel configuration in the leads.

  15. Ultrafast optical signal processing using semiconductor quantum dot amplifiers

    DEFF Research Database (Denmark)

    Berg, Tommy Winther; Mørk, Jesper

    2002-01-01

    The linear and nonlinear properties of quantum dot amplifiers are discussed on the basis of an extensive theoretical model. These devices show great potential for linear amplification as well as ultrafast signal processing.......The linear and nonlinear properties of quantum dot amplifiers are discussed on the basis of an extensive theoretical model. These devices show great potential for linear amplification as well as ultrafast signal processing....

  16. Isoniazid-induced psychosis in a patient on DOTS therapy

    Directory of Open Access Journals (Sweden)

    Imran Masood

    2011-01-01

    Full Text Available Acute psychosis induced by INH, especially when given as part of the DOTS regimen, has a variable presentation, and should always be kept in mind in the differential diagnosis. The diagnosis becomes especially challenging when the patient has tubercular meningitis or some other neurological disease. Here we present a case report of a patient who after 2 days of INH therapy under the DOTS regimen developed acute psychosis that resolved only after discontinuation of the drug.

  17. Dynamical symmetries in Kondo tunneling through complex quantum dots.

    Science.gov (United States)

    Kuzmenko, T; Kikoin, K; Avishai, Y

    2002-10-01

    Kondo tunneling reveals hidden SO(n) dynamical symmetries of evenly occupied quantum dots. As is exemplified for an experimentally realizable triple quantum dot in parallel geometry, the possible values n=3,4,5,7 can be easily tuned by gate voltages. Following construction of the corresponding o(n) algebras, scaling equations are derived and Kondo temperatures are calculated. The symmetry group for a magnetic field induced anisotropic Kondo tunneling is SU(2) or SO(4).

  18. Resonance fluorescence from quantum dots: beyond the Mollow triplet

    DEFF Research Database (Denmark)

    Lund, Anders Mølbjerg; Nielsen, Per Kær; Lorke, Michael;

    2011-01-01

    We show that the resonance fluorescence spectrum of a quantum dot excited by a strong pulse contains multiple peaks. An analytical model shows how the peak positions depend on pulse width and amplitude.......We show that the resonance fluorescence spectrum of a quantum dot excited by a strong pulse contains multiple peaks. An analytical model shows how the peak positions depend on pulse width and amplitude....

  19. Isoniazid-induced psychosis in a patient on DOTS therapy

    OpenAIRE

    Imran Masood; Sanjay Bhat; Aadil Beigh; Veena Gupta

    2011-01-01

    Acute psychosis induced by INH, especially when given as part of the DOTS regimen, has a variable presentation, and should always be kept in mind in the differential diagnosis. The diagnosis becomes especially challenging when the patient has tubercular meningitis or some other neurological disease. Here we present a case report of a patient who after 2 days of INH therapy under the DOTS regimen developed acute psychosis that resolved only after discontinuation of the drug.

  20. Quantum optics with quantum dots in photonic nanowires

    DEFF Research Database (Denmark)

    We will review recent studies performed on InAs quantum dots embedded in GaAs photonic wires, which highlight the strong interest of the photonic wire geometry for quantum optics experiments and quantum optoelectronic devices.......We will review recent studies performed on InAs quantum dots embedded in GaAs photonic wires, which highlight the strong interest of the photonic wire geometry for quantum optics experiments and quantum optoelectronic devices....

  1. Direct Interband Light Absorption in Conical Quantum Dot

    OpenAIRE

    Hayrapetyan, D. B.; Chalyan, A. V.; Kazaryan, E. M.; H. A. Sarkisyan

    2015-01-01

    In the framework of the adiabatic approximation, the energy states of electron as well as the direct light absorption are investigated in conical quantum dot. Analytical expressions for particle energy spectrum are obtained. The dependence of the absorption edge on geometrical parameters of conical quantum dot is obtained. Selection rules are revealed for transitions between levels with different quantum numbers. In particular, it is shown that for the radial quantum number transitions are al...

  2. Universal Parametric Correlations of Conductance Peaks in Quantum Dots

    OpenAIRE

    Alhassid, Y.; Attias, H.

    1996-01-01

    We compute the parametric correlation function of the conductance peaks in chaotic and weakly disordered quantum dots in the Coulomb blockade regime and demonstrate its universality upon an appropriate scaling of the parameter. For a symmetric dot we show that this correlation function is affected by breaking time-reversal symmetry but is independent of the details of the channels in the external leads. We derive a new scaling which depends on the eigenfunctions alone and can be extracted dir...

  3. Coulomb effects in tunneling through a quantum dot stack

    OpenAIRE

    Sprekeler, H.; Kiesslich, G.; Wacker, A; Schoell, E.

    2003-01-01

    Tunneling through two vertically coupled quantum dots is studied by means of a Pauli master equation model. The observation of double peaks in the current-voltage characteristic in a recent experiment is analyzed in terms of the tunnel coupling between the quantum dots and the coupling to the contacts. Different regimes for the emitter chemical potential indicating different peak scenarios in the tunneling current are discussed in detail. We show by comparison with a density matrix approach t...

  4. Shot Noise in Tunneling through a Quantum Dot Array

    OpenAIRE

    Kiesslich, G.; Wacker, A; Schoell, E.; Nauen, A.; Hohls, F.; Haug, R. J.

    2002-01-01

    The shot noise suppression in a sample containing a layer of self-assembled InAs quantum dots has been investigated experimentally and theoretically. The observation of a non-monotonic dependence of the Fano factor on the bias voltage in a regime where only few quantum dot ground states contribute to the tunneling current is analyzed by a master equation model. Under the assumption of tunneling through states without Coulomb interaction this behaviour can be qualitatively reproduced by an ana...

  5. Tip-enhanced fluorescence imaging of quantum dots

    OpenAIRE

    Huang, F.M.; Festy, F; Richards, D. R.

    2005-01-01

    We have imaged the fluorescence from a single quantum dot cluster using an apertureless scanning near-field optical microscope. When a sharp gold tip is brought within a few nanometers from the sample surface, the resulting enhancement in quantum dot fluorescence in the vicinity of the tip leads to a resolution of about 60 nm. We determine this enhancement of the fluorescence to be about fourfold in magnitude, which is consistent with the value expected as a result of competition between fluo...

  6. Time dependent quantum transport through Kondo correlated quantum dots

    OpenAIRE

    Goker, Ali; Gedik, Elif

    2013-01-01

    In this article, we review recent work about time dependent quantum transport through a quantum dot in Kondo regime. This represents a major step towards designing next generation transistors that are expected to replace current MOSFET's in a few years. We first discuss the effects of the density of states of gold contacts on the instantaneous conductance of an asymmetrically coupled quantum dot that is abruptly moved into Kondo regime via a gate voltage. Next, we investigate the effect of st...

  7. Noise and saturation properties of semiconductor quantum dot optical amplifiers

    DEFF Research Database (Denmark)

    Berg, Tommy Winther; Mørk, Jesper

    2002-01-01

    We present a detailed theoretical analysis of quantum dot optical amplifiers. Due to the presence of a reservoir of wetting layer states, the saturation and noise properties differ markedly from bulk or QW amplifiers and may be significantly improved.......We present a detailed theoretical analysis of quantum dot optical amplifiers. Due to the presence of a reservoir of wetting layer states, the saturation and noise properties differ markedly from bulk or QW amplifiers and may be significantly improved....

  8. Solution-Processed Nanocrystal Quantum Dot Tandem Solar Cells

    KAUST Repository

    Choi, Joshua J.

    2011-06-03

    Solution-processed tandem solar cells created from nanocrystal quantum dots with size-tuned energy levels are demonstrated. Prototype devices featuring interconnected quantum dot layers of cascaded energy gaps exhibit IR sensitivity and an open circuit voltage, V oc, approaching 1 V. The tandem solar cell performance depends critically on the optical and electrical properties of the interlayer. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Phonon-assisted decoherence and tunneling in quantum dot molecules

    DEFF Research Database (Denmark)

    Grodecka-Grad, Anna; Foerstner, Jens

    2011-01-01

    We study the influence of the phonon environment on the electron dynamics in a doped quantum dot molecule. A non-perturbative quantum kinetic theory based on correlation expansion is used in order to describe both diagonal and off-diagonal electron-phonon couplings representing real and virtual...... the quantum dots is studied in detail. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)...

  10. Progress in the toxicological researches for quantum dots

    Institute of Scientific and Technical Information of China (English)

    LI HongCheng; ZHOU QunFang; LIU Wei; YAN Bing; ZHAO Yibing; JIANG GuiBin

    2008-01-01

    Quantum dots (QDs) have Received more and more attention as a novel example of nanomaterials. Due to their unique fluorescent characteristics, quantum dots have been successfully applied in biotech-nology and medicine applications. Recently, the toxicity and the potential environmental effects of QDs have become a research hotspot. In this paper, toxicological effects of QDs are reviewed, and the prospects and research directions are given based on the analysis of this research field.

  11. Progress in the toxicological researches for quantum dots

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Quantum dots (QDs) have received more and more attention as a novel example of nanomaterials. Due to their unique fluorescent characteristics,quantum dots have been successfully applied in biotech-nology and medicine applications. Recently,the toxicity and the potential environmental effects of QDs have become a research hotspot. In this paper,toxicological effects of QDs are reviewed,and the prospects and research directions are given based on the analysis of this research field.

  12. Magnetization reversal in long chains of submicrometric Co dots

    OpenAIRE

    Martín, J.I.; Nogués i Sanmiquel, Josep; Schuller, Ivan K.; van Bael, M.J.; Temst, K; Van Haesendonck, C.; Moshchalkov, V. V.; Bruynseraede, Y.

    1998-01-01

    This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. Long chains of 400 nm diam Co dots prepared by combined electron-beam lithography exhibit interesting magnetotransport properties. The magnetoresistance of the chains of dots is markedly different from single Co films, indicating a strongly modified magnetization reversal process. Magnetic force microscopy(MFM) shows that, after magnetic saturat...

  13. Fluorescence from a quantum dot and metallic nanosphere hybrid system

    Energy Technology Data Exchange (ETDEWEB)

    Schindel, Daniel G. [Department of Mathematics and Statistics, University of Winnipeg, 515 Portage Avenue, Winnipeg, MB, R3B 2E9 (Canada); Singh, Mahi R. [Department of Physics and Astronomy, University of Western Ontario, 1151 Richmond Street, London, ON, N6A 3K7 (Canada)

    2014-03-31

    We present energy absorption and interference in a quantum dot-metallic nanosphere system embedded on a dielectric substrate. A control field is applied to induce dipole moments in the nanosphere and the quantum dot, and a probe field is applied to monitor absorption. Dipole moments in the quantum dot or the metal nanosphere are induced, both by the external fields and by each other's dipole fields. Thus, in addition to direct polarization, the metal nanosphere and the quantum dot will sense one another via the dipole-dipole interaction. The density matrix method was used to show that the absorption spectrum can be split from one peak to two peaks by the control field, and this can also be done by placing the metal sphere close to the quantum dot. When the two are extremely close together, a self-interaction in the quantum dot produces an asymmetry in the absorption peaks. In addition, the fluorescence efficiency can be quenched by the addition of a metal nanosphere. This hybrid system could be used to create ultra-fast switching and sensing nanodevices.

  14. Emission redistribution from a quantum dot-bowtie nanoantenna

    CERN Document Server

    Regler, A; Lyamkina, A; Spiegl, M; Müller, K; Vuckovic, J; Finley, J J; Kaniber, M

    2016-01-01

    We present a combined experimental and simulation study of a single self-assembled InGaAs quantum dot coupled to a nearby ($\\sim 25nm$) plasmonic antenna. Micro-photoluminescence spectroscopy shows a $\\sim 2.4\\times$ increase of intensity, which is attributed to spatial far-field redistribution of the emission from the quantum dot-antenna system. Power-dependent studies show similar saturation powers of $2.5\\mu W$ for both coupled and uncoupled quantum dot emission in polarization-resolved measurements. Moreover, time-resolved spectroscopy reveals the absence of Purcell-enhancement of the quantum dot coupled to the antenna as compared to an uncoupled dot, yielding comparable exciton lifetimes of $\\tau\\sim0.5ns$. This observation is supported by numerical simulations, suggesting only minor Purcell-effects of $25nm$. The observed increased emission from a coupled quantum dot-plasmonic antenna system is found to be in good qualitative agreement with numerical simulations and will lead to a better understanding o...

  15. Random Telegraph Signal in a Metallic Double-Dot System

    Science.gov (United States)

    Vardi, Yuval; Guttman, Avraham; Bar-Joseph, Israel

    2015-03-01

    Double quantum dot systems offer a unique opportunity for studying the world of quantum transport. This stems from the ability to localize an electron in a limited region in space on the dot, and monitor its presence and properties. Another system, in which electrons can be stored and measured, is an electronic trap in solid. The electrons in such a trap are better isolated from the environment. However, their measurement and control are more difficult. Here we demonstrate how these two systems, metallic double-dots and electronic traps, are combined to yield a hybrid structure in which an electron can be stored for long durations and can be easily detected and measured. We investigate the dynamics of a single electron surface trap, embedded in a self-assembly metallic double-dot system. The charging and discharging of the trap by a single electron is manifested as a random telegraph signal of the current through the double-dot device. We find that we can control the duration that an electron resides in the trap through the current, varying it between fractions of a second to more than an hour, at the Coulomb blockade region. We suggest that the observed switching is the electrical manifestation of the optical blinking phenomenon, commonly observed in semiconductor quantum dots. Y. Vardi, A. Guttman, and I. Bar-Joseph, Nano Lett. 14, 2794 (2014). [DOI: 10.1021/nl500803p

  16. Colloidal quantum dot photovoltaics: The effect of polydispersity

    KAUST Repository

    Zhitomirsky, David

    2012-02-08

    The size-effect tunability of colloidal quantum dots enables facile engineering of the bandgap at the time of nanoparticle synthesis. The dependence of effective bandgap on nanoparticle size also presents a challenge if the size dispersion, hence bandgap variability, is not well-controlled within a given quantum dot solid. The impact of this polydispersity is well-studied in luminescent devices as well as in unipolar electronic transport; however, the requirements on monodispersity have yet to be quantified in photovoltaics. Here we carry out a series of combined experimental and model-based studies aimed at clarifying, and quantifying, the importance of quantum dot monodispersity in photovoltaics. We successfully predict, using a simple model, the dependence of both open-circuit voltage and photoluminescence behavior on the density of small-bandgap (large-diameter) quantum dot inclusions. The model requires inclusion of trap states to explain the experimental data quantitatively. We then explore using this same experimentally tested model the implications of a broadened quantum dot population on device performance. We report that present-day colloidal quantum dot photovoltaic devices with typical inhomogeneous linewidths of 100-150 meV are dominated by surface traps, and it is for this reason that they see marginal benefit from reduction in polydispersity. Upon eliminating surface traps, achieving inhomogeneous broadening of 50 meV or less will lead to device performance that sees very little deleterious impact from polydispersity. © 2012 American Chemical Society.

  17. Large-area ordered Ge-Si compound quantum dot molecules on dot-patterned Si (001) substrates.

    Science.gov (United States)

    Lei, Hui; Zhou, Tong; Wang, Shuguang; Fan, Yongliang; Zhong, Zhenyang

    2014-08-29

    We report on the formation of large-area ordered Ge-Si compound quantum dot molecules (CQDMs) in a combination of nanosphere lithography and self-assembly. Truncated-pyramid-like Si dots with {11n} facets are readily formed, which are spatially ordered in a large area with controlled period and size. Each Si dot induces four self-assembled Ge-rich dots at its base edges that can be fourfold symmetric along directions. A model based on surface chemical potential accounts well for these phenomena. Our results disclose the critical effect of surface curvature on the diffusion and the aggregation of Ge adatoms and shed new light on the unique features and the inherent mechanism of self-assembled QDs on patterned substrates. Such a configuration of one Si QD surrounded by fourfold symmetric Ge-rich QDs can be seen as a CQDM with unique features, which will have potential applications in novel devices. PMID:25078348

  18. Magneto-optical absorption in semiconducting spherical quantum dots: Influence of the dot-size, confining potential, and magnetic field

    Directory of Open Access Journals (Sweden)

    Manvir S. Kushwaha

    2014-12-01

    Full Text Available Semiconducting quantum dots – more fancifully dubbed artificial atoms – are quasi-zero dimensional, tiny, man-made systems with charge carriers completely confined in all three dimensions. The scientific quest behind the synthesis of quantum dots is to create and control future electronic and optical nanostructures engineered through tailoring size, shape, and composition. The complete confinement – or the lack of any degree of freedom for the electrons (and/or holes – in quantum dots limits the exploration of spatially localized elementary excitations such as plasmons to direct rather than reciprocal space. Here we embark on a thorough investigation of the magneto-optical absorption in semiconducting spherical quantum dots characterized by a confining harmonic potential and an applied magnetic field in the symmetric gauge. This is done within the framework of Bohm-Pines’ random-phase approximation that enables us to derive and discuss the full Dyson equation that takes proper account of the Coulomb interactions. As an application of our theoretical strategy, we compute various single-particle and many-particle phenomena such as the Fock-Darwin spectrum; Fermi energy; magneto-optical transitions; probability distribution; and the magneto-optical absorption in the quantum dots. It is observed that the role of an applied magnetic field on the absorption spectrum is comparable to that of a confining potential. Increasing (decreasing the strength of the magnetic field or the confining potential is found to be analogous to shrinking (expanding the size of the quantum dots: resulting into a blue (red shift in the absorption spectrum. The Fermi energy diminishes with both increasing magnetic-field and dot-size; and exhibits saw-tooth-like oscillations at large values of field or dot-size. Unlike laterally confined quantum dots, both (upper and lower magneto-optical transitions survive even in the extreme instances. However, the intra

  19. Valérie Deplaigne, Les femmes nobles dans les conflits de transmission de biens aux lendemains de la bataille d’Azincourt, en pays de droit coutumier français

    Directory of Open Access Journals (Sweden)

    Valérie Deplaigne

    2008-07-01

    Full Text Available Faisant suite à un premier travail de recherche portant sur le patrimoine, l’héritage et la transmission des biens d’une héritière noble à la fin du XVe siècle, ce mémoire de deuxième année de Master a pour ambition de sortir de l’aspect monographique alors embrassé pour tenter une approche comparatiste à partir de l’étude de différents cas. Le cadre chronologique choisi est celui de « l’après-Azincourt », moment propice à la plus grande participation des femmes nobles à la vie publique et à ...

  20. Le bien-être au travail en mutation chez les enseignants - une nouvelle approche guidée par la théorie culturelle et historique de l’activité

    OpenAIRE

    Launis, Kirsti; Koli, Annarita

    2014-01-01

    De nombreuses recherches ont révélé que le stress et l’épuisement au travail des enseignants sont en progression. Il s’agit manifestement d’un grave problème constituant une menace pour leur santé et leur bien-être. Au cours de cette étude, les chercheurs ont mesuré les diverses sollicitations exercées dans le travail d’enseignantes et présenté des propositions pour améliorer leur travail et ses conditions de réalisation. Ces propositions ont été prises en compte dans des programmes de format...

  1. El derecho de compensación por trabajo doméstico en el régimen de separación de bienes del cc y en la LREMV: análisis comparativo

    OpenAIRE

    Montes Rodríguez, María Pilar

    2015-01-01

    La dedicación exclusiva de unos de los cónyuges al trabajo doméstico le atribuye, en el Código civil español, el derecho a una compensación económica cuando el régimen económico matrimonial es el de separación de bienes. En la LREMV el trabajo doméstico no sólo se considera contribución a las cargas del matrimonio sino que también da lugar a un derecho de compensación Exclusive dedication of one of the spouses to domestic work attributed to him in the Spanish Civil Code, ...

  2. Compact Interconnection Networks Based on Quantum Dots

    Science.gov (United States)

    Fijany, Amir; Toomarian, Nikzad; Modarress, Katayoon; Spotnitz, Matthew

    2003-01-01

    Architectures that would exploit the distinct characteristics of quantum-dot cellular automata (QCA) have been proposed for digital communication networks that connect advanced digital computing circuits. In comparison with networks of wires in conventional very-large-scale integrated (VLSI) circuitry, the networks according to the proposed architectures would be more compact. The proposed architectures would make it possible to implement complex interconnection schemes that are required for some advanced parallel-computing algorithms and that are difficult (and in many cases impractical) to implement in VLSI circuitry. The difficulty of implementation in VLSI and the major potential advantage afforded by QCA were described previously in Implementing Permutation Matrices by Use of Quantum Dots (NPO-20801), NASA Tech Briefs, Vol. 25, No. 10 (October 2001), page 42. To recapitulate: Wherever two wires in a conventional VLSI circuit cross each other and are required not to be in electrical contact with each other, there must be a layer of electrical insulation between them. This, in turn, makes it necessary to resort to a noncoplanar and possibly a multilayer design, which can be complex, expensive, and even impractical. As a result, much of the cost of designing VLSI circuits is associated with minimization of data routing and assignment of layers to minimize crossing of wires. Heretofore, these considerations have impeded the development of VLSI circuitry to implement complex, advanced interconnection schemes. On the other hand, with suitable design and under suitable operating conditions, QCA-based signal paths can be allowed to cross each other in the same plane without adverse effect. In principle, this characteristic could be exploited to design compact, coplanar, simple (relative to VLSI) QCA-based networks to implement complex, advanced interconnection schemes. The proposed architectures require two advances in QCA-based circuitry beyond basic QCA-based binary

  3. HA TRAÍDO HASTA NOSOTROS DESDE TERRITORIO ENEMIGO, EL ALUD DE LA GUERRA: CONFISCACIÓN DE MAQUINARIAS Y APROPIACIÓN DE BIENES CULTURALES DURANTE LA OCUPACIÓN DE LIMA, 1881-1883

    Directory of Open Access Journals (Sweden)

    Milton Godoy Orellana

    2011-12-01

    Full Text Available El artículo analiza la confiscación de maquinarias y la apropiación de bienes culturales durante la ocupación chilena de Lima. Ambos temas en la producción historiográfica de la Guerra del Pacífico no han sido trabajados en profundidad, siendo negados o soslayados, aun considerando la evidencia documental existente en Chile. Basándose principalmente en estos repositorios documentales, los temas señalados son el motivo central del presente artículo, analizando la situación peruana, la participación de oficiales y representantes del Estado chileno durante la ocupación y la respuesta en Chile frente a la llegada de los barcos con bienes culturales -libros, estatuas u ornamentos para espacios públicos-, que varió desde el encubrimiento mediante el eufemismo, hasta la crítica de la prensa nacional y el rotundo rechazo por parte de la Cámara de Diputados de Chile.This article analyzes the confiscation of machinery and the appropriation of cultural goods during the occupation of Lima. Both themes have not been explored in depth by the War of the Pacific historiography, being neglected or ignored even considering the documented evidence that exists in Chile. Based mainly on those documents the article analyzes the Peruvian situation, the participation of Chilean officials and State representatives during the occupation, the answer in Chile facing the arrival of ships with cultural goods -books, statutes and ornaments for public spaces- that varied from the covering up through euphemism, to the critique from the national press and the categorical rejection on the part of the Chilean House of Representatives.

  4. The DotA protein from Legionella pneumophila is secreted by a novel process that requires the Dot/Icm transporter

    OpenAIRE

    Nagai, Hiroki; Roy, Craig R.

    2001-01-01

    Legionella pneumophila requires the dot/icm genes to create an organelle inside eukaryotic host cells that will support bacterial replication. The dot/icm genes are predicted to encode a type IV-related secretion apparatus. However, no proteins have been identified that require the dot/icm genes for secretion. In this study we show that the DotA protein, which was previously found to be a polytopic membrane protein, is secreted by the Dot/Icm transporter into culture supernatants. Secreted Do...

  5. Ground State Transitions in Vertically Coupled Four-Layer Single Electron Quantum Dots

    Institute of Scientific and Technical Information of China (English)

    WANG An-Mei; XIE Wen-Fang

    2005-01-01

    We study a four-electron system in a vertically coupled four-layer quantum dot under a magnetic field by the exact diagonalization of the Hamiltonian matrix. We find that discontinuous ground-state energy transitions are induced by an external magnetic field. We find that dot-dot distance and electron-electron interaction strongly affect the low-lying states of the coupled quantum dots. The inter-dot correlation leads to some sequences of possible disappearances of ground state transitions, which are present for uncoupled dots.

  6. Ground State Transitions in Vertically Coupled Four-Layer Single Electron Quantum Dots

    Institute of Scientific and Technical Information of China (English)

    WANGAn-Mei; XIEWen-Fang

    2005-01-01

    We study a four-electron system in a vertically coupled four-layer quantum dot under a magnetic field by the exact diagonalization of the Hamiltonian matr/x. We find that discontinuous ground-state energy transitions are induced by an external magnetic field. We find that dot-dot distance and electron-electron interaction strongly affect the low-lying states of the coupled quantum dots. The inter-dot correlation leads to some sequences of possible disappearances of ground state transitions, which are present for uncoupled dots.

  7. Advancing colloidal quantum dot photovoltaic technology

    Directory of Open Access Journals (Sweden)

    Cheng Yan

    2016-06-01

    Full Text Available Colloidal quantum dots (CQDs are attractive materials for solar cells due to their low cost, ease of fabrication and spectral tunability. Progress in CQD photovoltaic technology over the past decade has resulted in power conversion efficiencies approaching 10%. In this review, we give an overview of this progress, and discuss limiting mechanisms and paths for future improvement in CQD solar cell technology.We briefly summarize nanoparticle synthesis and film processing methods and evaluate the optoelectronic properties of CQD films, including the crucial role that surface ligands play in materials performance. We give an overview of device architecture engineering in CQD solar cells. The compromise between carrier extraction and photon absorption in CQD photovoltaics is analyzed along with different strategies for overcoming this trade-off. We then focus on recent advances in absorption enhancement through innovative device design and the use of nanophotonics. Several light-trapping schemes, which have resulted in large increases in cell photocurrent, are described in detail. In particular, integrating plasmonic elements into CQD devices has emerged as a promising approach to enhance photon absorption through both near-field coupling and far-field scattering effects. We also discuss strategies for overcoming the single junction efficiency limits in CQD solar cells, including tandem architectures, multiple exciton generation and hybrid materials schemes. Finally, we offer a perspective on future directions for the field and the most promising paths for achieving higher device efficiencies.

  8. Colloidal quantum dot photodetectors (Presentation Recording)

    Science.gov (United States)

    Adinolfi, Valerio; Sargent, Edward H.

    2015-08-01

    Colloidal quantum dots (CQDs) are emerging solution processed materials combining low cost, easy deposition on large and flexible substrates, and bandgap tunability. The latter feature, which allows spectral tuning of the absorption profile of the semiconductor, makes these materials particularly attractive for light detection applications. Lead sulfide (PbS) CQDs, in particular, have shown astonishing performance as a light sensitive material operating at visible and infrared (IR) wavelengths. Early studies of PbS CQDs used as a photosensitive resistor (photoconductor) showed an impressive responsivity - exceeding 1000 A/W - and a detectivity (D*) higher then 10^13 Jones. This impressive D* was preserved in the successive development of the first PbS CQD photodiode, showing the possibility to realize fast - f_3db > 1Mhz - and sensitive IR detectors. Currently, the field is moving toward the development of hybrid devices and phototransitors. PbS CQDs have been combined in field effect transistors (FETs) with graphene and MoS2 channels, showing ultra-high gain (exceeding 10^8 electrons/photons) and high D*. Recently a photo-junction FET (photo-JFET) has been reported that breaks the inherent dark current/gain/bandwidth compromise affecting photoconductive light detectors. With this presentation we offer a broad overview on CQD photodetection highlighting the past achievements, the benefits, the challenges and the prospects for the future research on this field.

  9. Doping silicon nanocrystals and quantum dots

    Science.gov (United States)

    Oliva-Chatelain, Brittany L.; Ticich, Thomas M.; Barron, Andrew R.

    2016-01-01

    The ability to incorporate a dopant element into silicon nanocrystals (NC) and quantum dots (QD) is one of the key technical challenges for the use of these materials in a number of optoelectronic applications. Unlike doping of traditional bulk semiconductor materials, the location of the doping element can be either within the crystal lattice (c-doping), on the surface (s-doping) or within the surrounding matrix (m-doping). A review of the various synthetic strategies for doping silicon NCs and QDs is presented, concentrating on the efficacy of the synthetic routes, both in situ and post synthesis, with regard to the structural location of the dopant and the doping level. Methods that have been applied to the characterization of doped NCs and QDs are summarized with regard to the information that is obtained, in particular to provide researchers with a guide to the suitable techniques for determining dopant concentration and location, as well as electronic and photonic effectiveness of the dopant.

  10. Photodynamic antibacterial effect of graphene quantum dots.

    Science.gov (United States)

    Ristic, Biljana Z; Milenkovic, Marina M; Dakic, Ivana R; Todorovic-Markovic, Biljana M; Milosavljevic, Momir S; Budimir, Milica D; Paunovic, Verica G; Dramicanin, Miroslav D; Markovic, Zoran M; Trajkovic, Vladimir S

    2014-05-01

    Synthesis of new antibacterial agents is becoming increasingly important in light of the emerging antibiotic resistance. In the present study we report that electrochemically produced graphene quantum dots (GQD), a new class of carbon nanoparticles, generate reactive oxygen species when photoexcited (470 nm, 1 W), and kill two strains of pathogenic bacteria, methicillin-resistant Staphylococcus aureus and Escherichia coli. Bacterial killing was demonstrated by the reduction in number of bacterial colonies in a standard plate count method, the increase in propidium iodide uptake confirming the cell membrane damage, as well as by morphological defects visualized by atomic force microscopy. The induction of oxidative stress in bacteria exposed to photoexcited GQD was confirmed by staining with a redox-sensitive fluorochrome dihydrorhodamine 123. Neither GQD nor light exposure alone were able to cause oxidative stress and reduce the viability of bacteria. Importantly, mouse spleen cells were markedly less sensitive in the same experimental conditions, thus indicating a fairly selective antibacterial photodynamic action of GQD. PMID:24612819

  11. Photodynamic antibacterial effect of graphene quantum dots.

    Science.gov (United States)

    Ristic, Biljana Z; Milenkovic, Marina M; Dakic, Ivana R; Todorovic-Markovic, Biljana M; Milosavljevic, Momir S; Budimir, Milica D; Paunovic, Verica G; Dramicanin, Miroslav D; Markovic, Zoran M; Trajkovic, Vladimir S

    2014-05-01

    Synthesis of new antibacterial agents is becoming increasingly important in light of the emerging antibiotic resistance. In the present study we report that electrochemically produced graphene quantum dots (GQD), a new class of carbon nanoparticles, generate reactive oxygen species when photoexcited (470 nm, 1 W), and kill two strains of pathogenic bacteria, methicillin-resistant Staphylococcus aureus and Escherichia coli. Bacterial killing was demonstrated by the reduction in number of bacterial colonies in a standard plate count method, the increase in propidium iodide uptake confirming the cell membrane damage, as well as by morphological defects visualized by atomic force microscopy. The induction of oxidative stress in bacteria exposed to photoexcited GQD was confirmed by staining with a redox-sensitive fluorochrome dihydrorhodamine 123. Neither GQD nor light exposure alone were able to cause oxidative stress and reduce the viability of bacteria. Importantly, mouse spleen cells were markedly less sensitive in the same experimental conditions, thus indicating a fairly selective antibacterial photodynamic action of GQD.

  12. Advancing colloidal quantum dot photovoltaic technology

    Science.gov (United States)

    Cheng, Yan; Arinze, Ebuka S.; Palmquist, Nathan; Thon, Susanna M.

    2016-06-01

    Colloidal quantum dots (CQDs) are attractive materials for solar cells due to their low cost, ease of fabrication and spectral tunability. Progress in CQD photovoltaic technology over the past decade has resulted in power conversion efficiencies approaching 10%. In this review, we give an overview of this progress, and discuss limiting mechanisms and paths for future improvement in CQD solar cell technology.We briefly summarize nanoparticle synthesis and film processing methods and evaluate the optoelectronic properties of CQD films, including the crucial role that surface ligands play in materials performance. We give an overview of device architecture engineering in CQD solar cells. The compromise between carrier extraction and photon absorption in CQD photovoltaics is analyzed along with different strategies for overcoming this trade-off. We then focus on recent advances in absorption enhancement through innovative device design and the use of nanophotonics. Several light-trapping schemes, which have resulted in large increases in cell photocurrent, are described in detail. In particular, integrating plasmonic elements into CQD devices has emerged as a promising approach to enhance photon absorption through both near-field coupling and far-field scattering effects. We also discuss strategies for overcoming the single junction efficiency limits in CQD solar cells, including tandem architectures, multiple exciton generation and hybrid materials schemes. Finally, we offer a perspective on future directions for the field and the most promising paths for achieving higher device efficiencies.

  13. Optical nuclear spin polarization in quantum dots

    Science.gov (United States)

    Li, Ai-Xian; Duan, Su-Qing; Zhang, Wei

    2016-10-01

    Hyperfine interaction between electron spin and randomly oriented nuclear spins is a key issue of electron coherence for quantum information/computation. We propose an efficient way to establish high polarization of nuclear spins and reduce the intrinsic nuclear spin fluctuations. Here, we polarize the nuclear spins in semiconductor quantum dot (QD) by the coherent population trapping (CPT) and the electric dipole spin resonance (EDSR) induced by optical fields and ac electric fields. By tuning the optical fields, we can obtain a powerful cooling background based on CPT for nuclear spin polarization. The EDSR can enhance the spin flip-flop rate which may increase the cooling efficiency. With the help of CPT and EDSR, an enhancement of 1300 times of the electron coherence time can be obtained after a 10-ns preparation time. Project partially supported by the National Natural Science Foundations of China (Grant Nos. 11374039 and 11174042) and the National Basic Research Program of China (Grant Nos. 2011CB922204 and 2013CB632805).

  14. The ten deadly mistakes of wanna-dots.

    Science.gov (United States)

    Kanter, R M

    2001-01-01

    Increasingly, it seems, there are just two types of companies left in the world: dot-coms, born on the Internet, and "wanna-dots," established organizations that are seeking to incorporate the Internet into their businesses. Some wanna-dots manage the deep mind-shift required to cross the digital divide. These are the pacesetters--the first movers and fast followers that exhibit organizational curiosity and the desire to innovate. But most wanna-dots are laggards; they don't rise to the challenge with the same resolve. In a global research effort involving more than 800 companies, the author uncovered so many wanna-dots making the same kinds of mistakes that it almost seemed they were following a How Not to Change guide. In this article, Kanter creates just such a guide, offering ten pieces of antiadvice that expose the tendency of wanna-dots to make only cosmetic changes when deep transformation is required. Beyond delineating what not to do, Kanter serves up two examples of wanna-dots that got it right. First, Williams-Sonoma, which successfully made up for a slow start to create a strong Web presence. Second, Honeywell, a pacesetter led by e-believers from the start, which still found the road to the Web a challenging one. For companies not born digital, the fundamental problem is change. And the real place to look for change is not on the Internet but inside your company--at your own organizational culture and your attitude toward change.

  15. Detection of CdSe quantum dot photoluminescence for security label on paper

    Energy Technology Data Exchange (ETDEWEB)

    Isnaeni,, E-mail: isnaeni@lipi.go.id; Sugiarto, Iyon Titok [Research Center for Physics, Indonesian Institute of Science, Building 442 Puspiptek Serpong, South Tangerang, Banten, Indonesia 15314 (Indonesia); Bilqis, Ratu; Suseno, Jatmiko Endro [Department of Physics, Diponegoro University, Jl. Prof. Soedarto, Tembalang, Semarang, Indonesia 50275 (Indonesia)

    2016-02-08

    CdSe quantum dot has great potential in various applications especially for emitting devices. One example potential application of CdSe quantum dot is security label for anti-counterfeiting. In this work, we present a practical approach of security label on paper using one and two colors of colloidal CdSe quantum dot, which is used as stamping ink on various types of paper. Under ambient condition, quantum dot is almost invisible. The quantum dot security label can be revealed by detecting emission of quantum dot using photoluminescence and cnc machine. The recorded quantum dot emission intensity is then analyzed using home-made program to reveal quantum dot pattern stamp having the word ’RAHASIA’. We found that security label using quantum dot works well on several types of paper. The quantum dot patterns can survive several days and further treatment is required to protect the quantum dot. Oxidation of quantum dot that occurred during this experiment reduced the emission intensity of quantum dot patterns.

  16. Detection of CdSe quantum dot photoluminescence for security label on paper

    International Nuclear Information System (INIS)

    CdSe quantum dot has great potential in various applications especially for emitting devices. One example potential application of CdSe quantum dot is security label for anti-counterfeiting. In this work, we present a practical approach of security label on paper using one and two colors of colloidal CdSe quantum dot, which is used as stamping ink on various types of paper. Under ambient condition, quantum dot is almost invisible. The quantum dot security label can be revealed by detecting emission of quantum dot using photoluminescence and cnc machine. The recorded quantum dot emission intensity is then analyzed using home-made program to reveal quantum dot pattern stamp having the word ’RAHASIA’. We found that security label using quantum dot works well on several types of paper. The quantum dot patterns can survive several days and further treatment is required to protect the quantum dot. Oxidation of quantum dot that occurred during this experiment reduced the emission intensity of quantum dot patterns

  17. Phase diagram and low temperature scenario for a triangular triple dot system

    Science.gov (United States)

    Xiong, Yong-Chen; Wang, Wei-Zhong; Yang, Jun-Tao; Luo, Shi-Jun

    2016-01-01

    We present a triangular triple quantum dot (TTQD) system with two dots connected parallelly to one conduction lead, and investigate the phase diagram, the electric transport, and the temperature-dependent magnetic moment at half filling. When the hopping between two connected dots t12 = 0, and those between the connected dots and the side dot are symmetric t13 = t23, two connected dots form a spin triplet due to the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction mediated by the dot-lead coupling and/or the hopping t13 (t23). For t13 = 0, the triplet is partially screened by the conduction leads at low temperature. Both the connected dots and the side dot contribute to the magnetic moment of the system. For any definite t13, the triplet is totally screened by the conduction leads and the side dot, and the two-stage Kondo effect occurs. When t12 increases beyond a critical t12c, two connected dots form a spin singlet and decouple from the side dot. In this case, the Kondo peak is strongly suppressed, indicating zero conductance, and only the localized side dot contribute to the magnetic moment at low temperature. When t13 ≠ t23, we find a crossover as t12 increases, contrast to the first order transition of the symmetric case. Numerical renormalization group technique and physical arguments are used to obtain a detailed understanding of these problems.

  18. El bien entre Aristóteles y Freud: la inversión del pensamiento psicoanalítico en la dimensión ética. // The final good between Aristotle and Freud: psychoanalytical thought reversal in the ethical dimension.

    Directory of Open Access Journals (Sweden)

    Paula Andrea Pérez Herrera.

    2009-12-01

    Full Text Available Starting with a brief introduction to the philosophical conception of the final good and the good, the author presents Freud’s reversal from a psychoanalytical approach as shown by Lacan in Seminar 7, passing from the question of the good to the function of the good in the ethical dimension of psychoanalysis. // En el presente artículo se desarrolla un breve recorrido en la concepción filosófica de el bien y lo bueno, para exponer la inversión hecha por Freud desde el psicoanálisis y mostrada por Lacan en el Seminario 7, pasando de la cuestión de el bien a la función del bien en la dimensión ética del psicoanálisis.

  19. Spin qubits in quantum dots - beyond nearest-neighbour exchange

    Science.gov (United States)

    Vandersypen, Lieven

    The spin of a single electron is the canonical two-level quantum system. When isolated in a semiconductor quantum dot, a single electron spin provides a well-controlled and long-lived quantum bit. So far, two-qubit gates in this system have relied on the spin exchange interaction that arises when the wave functions of neighbouring electrons overlap. Furthermore, experimental demonstrations of controlled spin-exchange have been limited to 1D quantum dot arrays only. Here we explore several avenues for scaling beyond 1D arrays with nearest-neighbour coupling. First, we show that second-order tunnel processes allow for coherent spin-exchange between non-nearest neighbour quantum dots. The detuning of the intermediate quantum dot controls the frequency of the exchange-driven oscillations of the spins. Second, we demonstrate shuttling of electrons in quantum dot arrays preserving the spin projection for more than 500 hops. We use this technique to read out multiple spins in a way analogous to the operation of a CCD. Finally, we develop superconducting resonators that are resilient to magnetic field and with a predicted tenfold increase in vacuum electric field amplitudes. This makes coupling spin qubits via superconducting resonators in a circuit-QED approach a realistic possibility. Supported by ERC, FOM, NWO, IARPA, ARO, EU.

  20. Quantum Dot- and Aptamer-Based Nanostructures for Biological Applications

    Science.gov (United States)

    Meshik, Xenia

    Quantum dots are semiconductor nanoparticles that have gained popularity in optical and electronic applications in recent years. Aptamers are short man-made oligonucleotides with high binding affinity for a specific target. One part of this work presents an optical FRET-based sensor for K+ and Pb2+ consisting of a fluorescent quantum dot, an aptamer, and a gold nanoparticle quencher. Additionally, an electrochemical sensor for K+ and Pb2+ is also presented, which consists of an aptamer with an electron donor bound to graphene. Both sensors are shown to detect K+ and Pb2+ at concentrations critical for human health. The emission spectrum of the optical sensor is also shown to shift in response to strong electric fields. UV-excited TiO 2 quantum dots are also investigated for their ability to influence the dynamics of voltage gated ion channels in cells. It was found that the activation voltage is shifted in the presence of UV-excited TiO2 quantum dots. Electrostatic force measurements and theoretical calculations confirm that electric fields in TiO2 can in fact be optically induced. ZnO quantum dots are also synthesized and their optical and electrical properties are similarly investigated. Additionally, Raman and surface-enhanced Raman spectroscopy is used in this work to find previously-unknown spectra of the aptamer Apt-alphavbeta3 and the peptide thymosin-beta4.

  1. Sunlight assisted photodegradation by tin oxide quantum dots

    Science.gov (United States)

    Shajira, P. S.; Prabhu, V. Ganeshchandra; Bushiri, M. Junaid

    2015-12-01

    Rutile phase of SnO2 quantum dots of average size of 2.5 nm were synthesized at a growth temperature of 70 °C and characterized with XRD, TEM, FTIR and Raman analysis. The effective strain within the lattice of SnO2 quantum dots was calculated by Williamson-Hall method. The broad peaks in XRD as well as Raman spectra and the presence of Raman bands at 569 and 432 cm-1 are due to lower crystallinity of nanoparticles. The optical band gap of SnO2 quantum dots was increased to 3.75 eV attributed to the quantum size effect. SnO2 quantum dots were annealed in air atmosphere and the crystallite size of the particles increased with annealing temperature. Sunlight assisted photodegration property of SnO2 quantum dots was investigated with vanillin as a model system and it shows the photodegradation efficiency of 87%. The photoluminescence and photodegradation efficiency of nanocrystallite SnO2 decreases with increase of crystallite size contributed to the reduction in population of defects and surface area.

  2. Carbon dots from tryptophan doped glucose for peroxynitrite sensing

    Energy Technology Data Exchange (ETDEWEB)

    Simões, Eliana F.C. [CIQ-UP, Grupo de Ciências Biológicas e Bioanalíticas, Faculdade de Farmácia da Universidade de Coimbra, Pólo das Ciências da Saúde, 3000-548 Coimbra (Portugal); CIQ-UP, Departamento de Química, Faculdade de Ciências da Universidade do Porto, R. Campo Alegre 687, 4169-007 Porto (Portugal); Esteves da Silva, Joaquim C.G. [CIQ-UP, Departamento de Química, Faculdade de Ciências da Universidade do Porto, R. Campo Alegre 687, 4169-007 Porto (Portugal); Leitão, João M.M., E-mail: jleitao@ff.uc.pt [CIQ-UP, Grupo de Ciências Biológicas e Bioanalíticas, Faculdade de Farmácia da Universidade de Coimbra, Pólo das Ciências da Saúde, 3000-548 Coimbra (Portugal)

    2014-12-10

    Highlights: • Synthesis of tryptophan doped carbon dots. • Experimental design optimization of the tryptophan doped carbon dots synthesis. • Fluorescence sensing of peroxynitrite by tryptophan doped carbon dots. • Peroxynitrite quantification in serum samples by tryptophan doped carbon dots. - Abstract: Tryptophan doped carbon dots (Trp-CD) were microwave synthesized. The optimum conditions of synthesizing of the Trp-CD were established by response surface multivariate optimization methodologies and were the following: 2.5 g of glucose and 300 mg of tryptophan diluted in 15 mL of water exposed for 5 min to a microwave radiation of 700 W. Trp-CD have an average size of 20 nm, were fluorescent with a quantum yield of 12.4% and the presence of peroxynitrite anion (ONOO{sup −}) provokes quenching of the fluorescence. The evaluated analytical methodology for ONOO{sup −} detection shows a linear response range from 5 to 25 μM with a limit of detection of 1.5 μM and quantification of 4.9 μM. The capability of the ONOO{sup −} quantification was evaluated in standard solutions and in fortified serum samples.

  3. Ge dots and nanostructures grown epitaxially on Si

    Energy Technology Data Exchange (ETDEWEB)

    Baribeau, J-M [Institute for Microstructural Sciences, National Research Council Canada, Ottawa, ON, K1A 0R6 (Canada); Wu, X [Institute for Microstructural Sciences, National Research Council Canada, Ottawa, ON, K1A 0R6 (Canada); Rowell, N L [Institute for National Measurements Standards, National Research Council Canada, Ottawa, ON, K1A 0R6 (Canada); Lockwood, D J [Institute for Microstructural Sciences, National Research Council Canada, Ottawa, ON, K1A 0R6 (Canada)

    2006-03-01

    We review recent progress in the growth and characterization of Si{sub 1-x}Ge{sub x} islands and Ge dots on (001) Si. We discuss the evolution of the island morphology with Si{sub 1-x}Ge{sub x} coverage, and the effect of growth parameters or post-growth annealing on the shape of islands and dots. We outline some of the structural, vibrational, and optical properties of Si{sub 1-x}Ge{sub x} islands and review recent advances in the determination of their composition and strain distribution. In particular, we present an analytical electron transmission microscopy study of the Ge spatial distribution in Ge dots and Si /Si{sub 1-x}Ge{sub x} island superlattices grown by molecular beam epitaxy and ultra-high vacuum chemical vapour deposition. We describe the use of undulated Si{sub 1-x}Ge{sub x} island superlattices for infrared detection at telecommunication wavelengths. Finally, we discuss various approaches currently being investigated to engineer Si{sub 1-x}Ge{sub x} quantum dots and, in particular, control their size, density, and spatial distribution. As examples, we show how C pre-deposition on Si(001) can influence nucleation and growth of Ge islands and how low temperature Si homo-epitaxy can lead to a particular surface cusp morphology that may promote dot nucleation. (topical review)

  4. Non-blinking quantum dot with a plasmonic nanoshell resonator.

    Science.gov (United States)

    Ji, Botao; Giovanelli, Emerson; Habert, Benjamin; Spinicelli, Piernicola; Nasilowski, Michel; Xu, Xiangzhen; Lequeux, Nicolas; Hugonin, Jean-Paul; Marquier, Francois; Greffet, Jean-Jacques; Dubertret, Benoit

    2015-02-01

    Colloidal semiconductor quantum dots are fluorescent nanocrystals exhibiting exceptional optical properties, but their emission intensity strongly depends on their charging state and local environment. This leads to blinking at the single-particle level or even complete fluorescence quenching, and limits the applications of quantum dots as fluorescent particles. Here, we show that a single quantum dot encapsulated in a silica shell coated with a continuous gold nanoshell provides a system with a stable and Poissonian emission at room temperature that is preserved regardless of drastic changes in the local environment. This novel hybrid quantum dot/silica/gold structure behaves as a plasmonic resonator with a strong Purcell factor, in very good agreement with simulations. The gold nanoshell also acts as a shield that protects the quantum dot fluorescence and enhances its resistance to high-power photoexcitation or high-energy electron beams. This plasmonic fluorescent resonator opens the way to a new family of plasmonic nanoemitters with robust optical properties. PMID:25581887

  5. MULTIPLE EXCITON GENERATIONSOLAR CELLS USING CdSe QUANTUM DOTS

    Directory of Open Access Journals (Sweden)

    HAFTOM MESFIN GEBRESLASSIE,

    2011-03-01

    Full Text Available Experimental and Simulation works of Nano structured Solar Cells Using CdSe Quantum Dots have been analyzed and investigated. CdSe quantum dots have been synthesized from non coordinating and highboiling solvent Octadecene and a series of increasing CdSe particle sizes are produced. The synthesized CdSe quantum dots are highly examined under a Transmission Electron Microscope and four images ofdifferent sizes of CdSe quantum dots (5.8 nm, 6.4 nm, 7.0 nm and 7.7 nm have been obtained. A 1.1x1.1cm2 TiO2 electrode is prepared using indium tin oxide conducting glass and TiO2 nanoparticles. The CdSe quantum dot (5.8nm was adsorbed on TiO2 photoelectrode and used as sensitizer. In this paper work, a sandwich type cell configuration which is made up of TiO2 photoelectrode, graphite coated counter electrode, an electrolyte of iodine and potassium iodide have been used. This sandwich type cell has been exposed to sun light and we have achieved 0.32 V and 0.2 mA

  6. Manipulating surface diffusion and elastic interactions to obtain quantum dot multilayer arrangements over different length scales

    Energy Technology Data Exchange (ETDEWEB)

    Placidi, E., E-mail: ernesto.placidi@ism.cnr.it; Arciprete, F. [Istituto di Struttura della Materia, CNR, Via del Fosso del Cavaliere 100, 00133 Rome (Italy); Università di Roma “Tor Vergata”, Dipartimento di Fisica, via della Ricerca Scientifica 1, 00133 Rome (Italy); Latini, V.; Latini, S.; Patella, F. [Università di Roma “Tor Vergata”, Dipartimento di Fisica, via della Ricerca Scientifica 1, 00133 Rome (Italy); Magri, R. [Dipartimento di Scienze Fisiche, Informatiche e Matematiche (FIM), Università di Modena e Reggio Emilia, and Centro S3 CNR-Istituto Nanoscienze, Via Campi 213/A, 4100 Modena (Italy); Scuderi, M.; Nicotra, G. [CNR-IMM, Strada VIII, 5, 95121 Catania (Italy)

    2014-09-15

    An innovative multilayer growth of InAs quantum dots on GaAs(100) is demonstrated to lead to self-aggregation of correlated quantum dot chains over mesoscopic distances. The fundamental idea is that at critical growth conditions is possible to drive the dot nucleation only at precise locations corresponding to the local minima of the Indium chemical potential. Differently from the known dot multilayers, where nucleation of new dots on top of the buried ones is driven by the surface strain originating from the dots below, here the spatial correlations and nucleation of additional dots are mostly dictated by a self-engineering of the surface occurring during the growth, close to the critical conditions for dot formation under the fixed oblique direction of the incoming As flux, that drives the In surface diffusion.

  7. Theranostic carbon dots derived from garlic with efficient anti-oxidative effects towards macrophages

    DEFF Research Database (Denmark)

    Yang, Chuanxu; Ogaki, Ryosuke; Hansen, Line;

    2015-01-01

    Luminescent garlic carbon dots with superior photostability are synthesized via microwave assisted heating. The garlic dots are biocompatible, have low toxicity and can be used as benign theranostic nanoparticles for bioimaging with efficient anti-oxidative effects towards macrophages....

  8. A Quantum Dot with Spin-Orbit Interaction--Analytical Solution

    Science.gov (United States)

    Basu, B.; Roy, B.

    2009-01-01

    The practical applicability of a semiconductor quantum dot with spin-orbit interaction gives an impetus to study analytical solutions to one- and two-electron quantum dots with or without a magnetic field.

  9. Si quantum dot structures and their applications

    Science.gov (United States)

    Shcherbyna, L.; Torchynska, T.

    2013-06-01

    This paper presents briefly the history of emission study in Si quantum dots (QDs) in the last two decades. Stable light emission of Si QDs and NCs was observed in the spectral ranges: blue, green, orange, red and infrared. These PL bands were attributed to the exciton recombination in Si QDs, to the carrier recombination through defects inside of Si NCs or via oxide related defects at the Si/SiOx interface. The analysis of recombination transitions and the different ways of the emission stimulation in Si QD structures, related to the element variation for the passivation of surface dangling bonds, as well as the plasmon induced emission and rare earth impurity activation, have been presented. The different applications of Si QD structures in quantum electronics, such as: Si QD light emitting diodes, Si QD single union and tandem solar cells, Si QD memory structures, Si QD based one electron devices and double QD structures for spintronics, have been discussed as well. Note the significant worldwide interest directed toward the silicon-based light emission for integrated optoelectronics is related to the complementary metal-oxide semiconductor compatibility and the possibility to be monolithically integrated with very large scale integrated (VLSI) circuits. The different features of poly-, micro- and nanocrystalline silicon for solar cells, that is a mixture of both amorphous and crystalline phases, such as the silicon NCs or QDs embedded in a α-Si:H matrix, as well as the thin film 2-cell or 3-cell tandem solar cells based on Si QD structures have been discussed as well. Silicon NC based structures for non-volatile memory purposes, the recent studies of Si QD base single electron devices and the single electron occupation of QDs as an important component to the measurement and manipulation of spins in quantum information processing have been analyzed as well.

  10. Nitrogen-Doped Carbon Dots as A New Substrate for Sensitive Glucose Determination

    OpenAIRE

    Hanxu Ji; Feng Zhou; Jiangjiang Gu; Chen Shu; Kai Xi; Xudong Jia

    2016-01-01

    Nitrogen-doped carbon dots are introduced as a novel substrate suitable for enzyme immobilization in electrochemical detection metods. Nitrogen-doped carbon dots are easily synthesised from polyacrylamide in just one step. With the help of the amino group on chitosan, glucose oxidase is immobilized on nitrogen-doped carbon dots-modified carbon glassy electrodes by amino-carboxyl reactions. The nitrogen-induced charge delocalization at nitrogen-doped carbon dots can enhance the electrocatalyti...

  11. Double-layer-gate architecture for few-hole GaAs quantum dots

    Science.gov (United States)

    Wang, D. Q.; Hamilton, A. R.; Farrer, I.; Ritchie, D. A.; Klochan, O.

    2016-08-01

    We report the fabrication of single and double hole quantum dots using a double-layer-gate design on an undoped accumulation mode {{Al}}x{{Ga}}1-x{As}/GaAs heterostructure. Electrical transport measurements of a single quantum dot show varying addition energies and clear excited states. In addition, the two-level-gate architecture can also be configured into a double quantum dot with tunable inter-dot coupling.

  12. Quantum Size- Dependent Third- Order Nonlinear Optical Susceptibility in Semiconductor Quantum Dots

    Institute of Scientific and Technical Information of China (English)

    SUN Ting; XIONG Gui-guang

    2005-01-01

    The density matrix approach has been employed to investigate the optical nonlinear polarization in a single semiconductor quantum dot(QD). Electron states are considered to be confined within a quantum dot with infinite potential barriers. It is shown, by numerical calculation, that the third-order nonlinear optical susceptibilities for a typical Si quantum dot is dependent on the quantum size of the quantum dot and the frequency of incident light.

  13. Full characterization of a carbon nanotube based parallel double quantum dot

    OpenAIRE

    Abulizi, Gulibusitan; Baumgartner, Andreas; Schönenberger, Christian

    2016-01-01

    We have measured the differential conductance of a parallel carbon nanotube (CNT) double quantum dot (DQD) with strong inter-dot capacitance and inter-dot tunnel coupling. Nominally, the device consists of a single CNT with two contacts. However, we identify two sets of Coulomb blockade (CB) diamonds that do not block transport individually, which suggests that two quantum dots (QDs) are contacted in parallel. We find strong and periodic anti-crossings in the gate and bias dependence, which a...

  14. Coupling of self-assembled InAs quantum dots to surface plasmon polaritons

    DEFF Research Database (Denmark)

    Andersen, Mads Lykke; Stobbe, Søren; Johansen, Jeppe;

    2008-01-01

    InAs quantum dots have been placed at different distances to a silver mirror. We extract the coupling of quantum dots to surface plasmon polaritons as a function of the distance by time-resolved spontaneous emission measurements.......InAs quantum dots have been placed at different distances to a silver mirror. We extract the coupling of quantum dots to surface plasmon polaritons as a function of the distance by time-resolved spontaneous emission measurements....

  15. Scaling of the Coulomb Energy Due to Quantum Fluctuations in the Charge on a Quantum Dot

    DEFF Research Database (Denmark)

    Molenkamp, L. W; Flensberg, Karsten; Kemerink, M.

    1995-01-01

    The charging energy of a quantum dot is measured through the effect of its potential on the conductance of a second dot. This technique allows a measurement of the scaling of the dot's charging energy with the conductance of the tunnel barriers leading to the dot. We find that the charging energy...... scales quadratically with the reflection probability of the barriers. The observed power law agrees with a recent theory....

  16. Strain-controlled correlation effects in self-assembled quantum dot stacks

    OpenAIRE

    Kunert, R; Schoell, E.

    2006-01-01

    We show that elastic interactions of an array of self-assembled quantum dots in a parent material matrix are markedly distinct from the elastic field created by a single point defect, and can explain the observed abrupt correlation--anticorrelation transition in semiconductor quantum dot stacks. Finite volume effects of the quantum dots are shown to lead to sharper transitions. Our analysis also predicts the inclination angle under which the alignment in successive quantum dot layers occurs i...

  17. Double-layer-gate architecture for few-hole GaAs quantum dots.

    Science.gov (United States)

    Wang, D Q; Hamilton, A R; Farrer, I; Ritchie, D A; Klochan, O

    2016-08-19

    We report the fabrication of single and double hole quantum dots using a double-layer-gate design on an undoped accumulation mode [Formula: see text]/GaAs heterostructure. Electrical transport measurements of a single quantum dot show varying addition energies and clear excited states. In addition, the two-level-gate architecture can also be configured into a double quantum dot with tunable inter-dot coupling. PMID:27389108

  18. Colloidal Quantum Dot Photovoltaics Enhanced by Perovskite Shelling.

    Science.gov (United States)

    Yang, Zhenyu; Janmohamed, Alyf; Lan, Xinzheng; García de Arquer, F Pelayo; Voznyy, Oleksandr; Yassitepe, Emre; Kim, Gi-Hwan; Ning, Zhijun; Gong, Xiwen; Comin, Riccardo; Sargent, Edward H

    2015-11-11

    Solution-processed quantum dots are a promising material for large-scale, low-cost solar cell applications. New device architectures and improved passivation have been instrumental in increasing the performance of quantum dot photovoltaic devices. Here we report photovoltaic devices based on inks of quantum dot on which we grow thin perovskite shells in solid-state films. Passivation using the perovskite was achieved using a facile solution ligand exchange followed by postannealing. The resulting hybrid nanostructure created a more intrinsic CQD film, which, when incorporated into a photovoltaic device with graded bandstructure, achieved a record solar cell performance for single-step-deposited CQD films, exhibiting an AM1.5 solar power conversion efficiency of 8.95%.

  19. Nonradiative recombination of excitons in semimagnetic quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Chernenko, A. V., E-mail: chernen@issp.ac.ru [Russian Academy of Sciences, Institute of Solid State Physics (Russian Federation)

    2015-12-15

    The mechanisms of the nonradiative recombination of excitons in neutral and charged quantum dots based on II–VI semimagnetic semiconductors are investigated. It is shown that, along with the dipole–dipole and direct-exchange mechanisms, there is one more mechanism referred to as the indirect-exchange mechanism and related to sp–d mixing. The selection rules for nonradiative recombination by exchange mechanisms are subsequently derived. The dependence of the efficiency of all recombination mechanisms on the quantum-dot size is studied. The experimentally observed growth in the intracenter photoluminescence intensity with decreasing size of dots and nanocrystals is accounted for. Methods for experimental determination of the contributions of different mechanisms to nonradiative recombination are discussed.

  20. Folded-light-path colloidal quantum dot solar cells.

    KAUST Repository

    Koleilat, Ghada I

    2013-01-01

    Colloidal quantum dot photovoltaics combine low-cost solution processing with quantum size-effect tuning to match absorption to the solar spectrum. Rapid advances have led to certified solar power conversion efficiencies of over 7%. Nevertheless, these devices remain held back by a compromise in the choice of quantum dot film thickness, balancing on the one hand the need to maximize photon absorption, mandating a thicker film, and, on the other, the need for efficient carrier extraction, a consideration that limits film thickness. Here we report an architecture that breaks this compromise by folding the path of light propagating in the colloidal quantum dot solid. Using this method, we achieve a substantial increase in short-circuit current, ultimately leading to improved power conversion efficiency.