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Sample records for c71 dot bien

  1. Cómo nadar bien

    OpenAIRE

    Navarro Valdivielso, Fernando; Díaz Ureña, Germán; González Vegas, Manuel J.

    2012-01-01

    Nadar bien o mejor es la pretensión final de este libro. Al proceso que se propone para este objetivo lo hemos denominado método NB (Nadar bien). Nuestro interés se centra en que todos los interesados y practicantes en la natación puedan perfeccionar su técnica y disfrutar del dominio de la técnica.

  2. 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...

  3. 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...

  4. 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...

  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. Hard X-Ray Detection of the High Redshift Quasar 4C 71.07

    Science.gov (United States)

    Malizia, A.; Bassani, L.; Dean, A. J.; McCollough, M. L.; Stephen, J. B.; Zhang, S. N.

    1999-01-01

    BATSE/OSSE observations of the high redshift quasar 4C 71.07 indicate that this is the brightest and furthest AGN so far detected 20 keV. BATSE Earth occultation data have been used to search for emission from 4C 71.07 from nearly 3 years of observation. The mean source flux over the- whole period in the BATSE energy range 20-100 keV is (13.2 +/- 1.06) x 10(exp -11) erg/square cm/s corresponding to a luminosity of 2 x 10(exp 48 erg/s. The BATSE light curve over the 3 years of observations shows several flare-like events, one of which (in January 1996) is associated with an optical flare (R=16.1) but with a delay of 55 days. The OSSE/BATSE spectral analysis indicates that the source is characterized by a flat power spectrum (Gamma is approximately 1.1- 1.3) when in a low state: this spectral form is consistent within errors with the ASCA and ROSAT spectra. This means that the power law observed from 0.1 to 10 keV extends up to at least 1 MeV but steepens soon after to meet EGRET high energy data. BATSE data taken around the January 1996 flare suggests that the spectrum could be steeper when the source is in a bright state. The upsilon-F-upsilon representation of the source is typical of a low frequency peaked/ gamma- ray dominated blazar, with the synchrotron peak in the mm-FIR band and the Compton peak in the MeV band. The BATSE and OSSE spectral data seem to favour a model in which the high energy - flux is due to the sum of the synchrotron self-Compton and the external Compton contributions: this is also supported by the- variability behaviour of the source.

  10. 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.

  11. 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

  12. Biene und Honig im pharaonischen Ägypten

    OpenAIRE

    Feierabend, Birgit Sonja

    2009-01-01

    Ziel der Dissertation war es, eine Gesamtbetrachtung der altägyptischen Bienenhaltung zu geben, die Bedeutung der Biene herauszuarbeiten und den Gebrauch des Honigs im alten Ägypten vorzustellen. Darüber hinaus wurde die Herkunft und Zusammensetzung des Honigs untersucht sowie ein Vergleich mit der Bienenhaltung in den Nachbarländern gezogen. rnrnDie Biene ist mehrfach als Symbol oder Dekorationselement vorzufinden. Bereits am Ende des Alten Reiches, einem Zeitpunkt, als sich die Domestikatio...

  13. 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 ...

  14. 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.

  15. 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...

  16. Quantum dots

    CERN Document Server

    Borovitskaya, Elena

    2002-01-01

    In this book, leading experts on quantum dot theory and technology provide comprehensive reviews of all aspects of quantum dot systems. The following topics are covered: (1) energy states in quantum dots, including the effects of strain and many-body effects; (2) self-assembly and self-ordering of quantum dots in semiconductor systems; (3) growth, structures, and optical properties of III-nitride quantum dots; (4) quantum dot lasers. Contents: Low-Dimensional Systems (E Borovitskaya & M S Shur); Energy States in Quantum Dots (A J Williamson); Self-Organized Quantum Dots (A R Woll et al.); Grow

  17. 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...

  18. Reconsiderando las tecnologías sociales como bienes comunes

    Directory of Open Access Journals (Sweden)

    Ariel Vercelli

    2010-05-01

    Full Text Available En este artículo se describen las relaciones que se plantean entre las regulaciones sobre bienes materiales e intelectuales y las “tecnologías sociales”. Para ello, se utilizan algunas herramientas teórico-metodológicas provenientes del análisis socio-técnico y se aprovechan desarrollos conceptuales referidos a la caracterización de los “bienes comunes”. El artículo es parte de un ejercicio teórico donde las tecnologías sociales se consideran como bienes comunes. Con ello se busca problematizar el carácter jurídico-político que pueden adquirir algunas tecnologías sociales y, a su vez, analizar posibles formas de privatización y apropiación que éstas podrían sufrir por parte de corporaciones comerciales y Estados. In this article, the author describes relations proposed between the regulation of material and intellectual goods and the “social technologies.” To that end, theoretical-methodological tools from social-technical analysis are used, and conceptual developments related to the characterization of “common goods” are applied. The article is part of a theoretical exercise in which social technologies are taken to be common goods. For that purpose, the legal-political character that some social technologies may acquire is problematized, and, at the same time possible forms of privatization and appropriation that these might undergo by private business or the state are analyzed.

  19. 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...

  20. 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

  1. 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...

  2. 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;}

  3. 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.

  4. 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.

  5. 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

  6. La comunidad de bienes como forma jurídica de empresa

    OpenAIRE

    Vaticón Fernández, José Antonio

    2014-01-01

    Este trabajo trata sobre la Comunidad de Bienes, regulada en el los artículos 396 al 406 del Código Civil. Las características que definen a una Comunidad Bienes son las siguientes: 1. No tiene personalidad jurídica propia. 2. Hace falta un contrato privado para poder ejercer la actividad. 3. No se exige una aportación mínima de dinero. 4. Se exige un mínimo de dos socios. 5. La responsabilidad hacia terceros es ilimitada. En conclusión, la Comunidad de Bienes no es la...

  7. 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...

  8. Graphene composite for improvement in the conversion efficiency of flexible poly 3-hexyl-thiophene:[6,6]-phenyl C71 butyric acid methyl ester polymer solar cells

    International Nuclear Information System (INIS)

    The solution of thin graphene-sheets obtained from a simple ultrasonic exfoliation process was found to chemically interact with [6,6]-phenyl C71 butyric acid methyl ester (PCBM) molecules. The thinner graphene-sheets have significantly altered the positions of highest occupied molecular orbital and lowest unoccupied molecular orbital of PCBM, which is beneficial for the enhancement of the open circuit voltage of the solar cells. Flexible bulk heterojunction solar cells fabricated using poly 3-hexylthiophene (P3HT):PCBM-graphene exhibited a power conversion efficiency of 2.51%, which is a ∼2-fold increase as compared to those fabricated using P3HT:PCBM. Inclusion of graphene-sheets not only improved the open-circuit voltage but also enhanced the short-circuit current density owing to an improved electron transport

  9. 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.

  10. 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....

  11. 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...

  12. 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.

  13. VALORACIÓN ECONÓMICA DE BIENES AMBIENTALES POR BENEFICIARIOS CIRCUNDANTES Y NO CIRCUNDANTES

    Directory of Open Access Journals (Sweden)

    Mauricio G Villena

    2013-06-01

    Full Text Available La pregunta básica de investigación detrás de este trabajo es cómo difiere la valoración económica de un bien ambiental considerando beneficiarios circundantes (quienes viven cerca del bien en cuestión y no circundantes (quienes habitando el país donde se encuentra el bien, viven en poblaciones distantes y por tanto disfrutan esporádicamente de los beneficios provistos por el bien ambiental. En particular, en este documento se valora económicamente el Bosque de Algarrobos de la comunidad de Tiataco (Bolivia, realizando un análisis comparativo entre beneficiarios circundantes (familias residentes en la comunidad de Tiataco y beneficiarios no circundantes (familias residentes en la ciudad de Cochabamba, a 35 Km de Tiataco, a través del Método de Valoración Contingente con formato binario. Se estimaron medidas de cambio en el bienestar para ambos grupos, empleando estimaciones paramétricas y no paramétricas. Posteriormente, estas medidas se compararon estadísticamente por medio de la construcción de intervalos de confianza (entre estimaciones paramétricas y no paramétricas de cada población y entre ambas poblaciones. Por último, se identificaron los componentes del valor económico total que los beneficiarios tanto circundantes como no circundantes asignaron al bosque.

  14. Notas sobre Pasinetti, los bienes autoreproducibles y el “factor” trabajo

    OpenAIRE

    Alfons Barceló

    2006-01-01

    Esta nota pretende mostrar que son insatisfactorios los supuestos asumidos por Pasinetti sobre a) la presunta irrelevancia económica de las tasas propias de reproducción de los bienes autorreproducibles; b) la conceptualización del “trabajo” como “factor último de la producción”.

  15. 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.

  16. 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.

  17. 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...... of quantum dots, however, results in a large inhomogeneous broadening of quantum dot spectra. Work on self-assembled InGaAs/GaAs quantum dots will be presented. Properties of atom-like single-dot states are investigated optically using high spatial and spectral resolution. Single-dot spectra can be used...

  18. 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...... of quantum dots, however, results in a large inhomogeneous broadening of quantum dot spectra.Work on self-assembled InGaAs/GaAs quantum dots will be presented. Properties of atom-like single-dots states are investigated optically using high spatial and spectral resolution. Single-dot spectra can be used...

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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...

  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. 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

  7. 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...

  8. 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...

  9. 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...

  10. 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.

  11. 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...

  12. 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.

  13. 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...

  14. Aux vrais beaux biens : souvenirs autour de Max Ophuls

    OpenAIRE

    Müller, Martina

    2007-01-01

    En 1989 j’ai interrogé des collaborateurs de Max Ophuls qui avaient travaillé avec lui au théâtre, à la radio et au cinéma. Ces entretiens ont été enregistrés pour mon documentaire de quatre-vingt dix minutes : Max Ophuls. Aux vrais beaux biens, produit par la Westdeutscher Rundfunk, télévision allemande de Cologne. Cette émission – diffusée en 1990 et jamais présenté en France – est composée d’interviews et de commentaires de séquences. En outre on y entend la voix de Max Ophuls et on le voi...

  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. 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...

  17. "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...

  18. Programas políticos y bienes y usos comunales en Lorena durante la Revolución Francesa

    OpenAIRE

    Ríos, Manuel

    2015-01-01

    La historiografía inglesa ha ahondado en el estudio de los bienes y usos comunales con el propósito de comprender el rol que jugó la transformación de los mismos en la transición del feudalismo al capitalismo. No obstante, su contraparte francesa ha tendido a relegar este tipo de estudios a un segundo plano, sobre todo en lo que a los usos comunales respecta. De hecho, en los últimos veinte años se ha postulado la necesidad de estudiar a los bienes y usos comunales por separado, compartimenta...

  19. 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.

  20. 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

  1. Quantum Dots: Theory

    OpenAIRE

    Vukmirovic, Nenad

    2010-01-01

    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.

  2. El emprendimiento y el bien común: ¿competencias complementarias o excluyentes?

    Directory of Open Access Journals (Sweden)

    Juan David Enciso-Congote

    2010-04-01

    Full Text Available Este trabajo propone un análisis comparativo entre los requerimientos de la formación de competencias para el emprendimiento y para el desempeño laboral, de acuerdo con el escenario que sirve de contexto a cada una de ellas. En el caso del desempeño laboral, se toma como punto de referencia la estructura burocrática descrita por Max Weber. En cuanto al emprendimiento, las raíces son antropológicas, la naturaleza humana, independientemente de cualquier referente cultural o histórico. Estas consideraciones proporcionan un marco de referencia para reflexionar sobre las dificultades conceptuales y pedagógicas que obstaculizan la construcción de una visión más inclusiva de lo público y del compromiso que debe tener un profesional con la búsqueda del bien común y, por tanto, de la responsabilidad que recae en la formación universitaria para procurar este cometido.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. Bienes rústicos de aprovechamiento público en la Valencia moderna

    Directory of Open Access Journals (Sweden)

    David BERNABÉ GIL

    2009-12-01

    Full Text Available RESUMEN: Analiza el presente trabajo diversos aspectos relacionados con los derechos de aprovechamiento público que confluían en los espacios rústicos no cultivados del antiguo Reino de Valencia, así como la naturaleza de los problemas que solía suscitar su atribución dominical, dada la frecuente superposición de instancias institucionales con pretensiones de control. A partir de la compleja tipología que la casuística al respecto —aún escasa y mal conocida— permite entrever, queda en evidencia el fuerte arraigo de los elementos de regulación municipal vigentes en el realengo, si bien en franco retroceso ante los tardíos intentos de control por el Real Patrimonio. En los señoríos, sin embargo, son los derechos del titular de la jurisdicción los que consiguen prevalecer, aunque no necesariamente por exclusión de los reconocidos a la comunidad.ABSTRACT: This study analyzes different aspects related to the rights of public usage with regard to uncultivated agricultural spaces in the ancient Kingdom of Valencia, as well as the nature of the problems normally arising from the conferring of their feudal status, due to the frequent superimposing of institutional requests to gain control. With regard to the complex typology that the corresponding casuistry (still scarce and hardly known suggests, we can highlight the fact that the elements of municipal regulation that existed within the state were well-established, although they were clearly in decline in the face of the Royal Trust's late attempts to gain control. However, as regards the estates, the ownership rights of the jurisdiction were the ones that finally prevailed, although not necessarily by excluding the rights of the community.

  8. Quantum Dots for Biophotonics

    OpenAIRE

    Ken-Tye Yong

    2012-01-01

    This theme issue provides an excellent collection of reviews and original research articles on the study of various bioconjugated quantum dot formulations for diagnostics and therapy applications using biophotonic imaging and sensing approaches.

  9. 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

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

    OpenAIRE

    Somsak Panyakeow

    2010-01-01

    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 late...

  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. Bien commun, conflits d’intérêts et délibération éthique

    OpenAIRE

    Müller, Denis

    2016-01-01

    Si la notion de bien commun paraît de prime abord trop ambitieuse, trompeuse en ses promesses excessives et inaccessibles, elle est néanmoins nécessaire au débat éthique dans l’espace public contemporain. Cette contribution veut montrer comment une compréhension critique de la notion controversée de bien commun peut s’avérer compatible avec une prise en compte réaliste et responsable des conflits d’intérêts et de la délibération éthique. L’exemple du débat français sur la laïcité permet à cet...

  14. 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

  15. "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.

  16. 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.

  17. Evaluación de riesgos en el sector de fabricación de bienes de equipo

    OpenAIRE

    González Antuña, Pablo

    2013-01-01

    El propósito fundamental de este trabajo es orientar a todo el personal que trabaja en el sector de fabricación de bienes de equipo, sobre las condiciones de trabajo, las condiciones de las instalaciones a través de una evaluación de riesgos laborales presentes en las áreas de trabajo de dicho sector y sobre las medidas preventivas a adoptar para controlar el riesgo laboral

  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. Economía, bienes públicos puros e Internet : revelando el caso del FLOSS (“Free/Libre Open Source Software” o “Software Libre y Software de Código Abierto”)

    OpenAIRE

    Soler Muñoz, Rafael

    2013-01-01

    Desde que Paul Samuelson publicase en 1954 su obra “The pure theory of public expenditure”, diferenciando los bienes económicos entre bienes públicos y bienes privados, ha existido controversia sobre la posibilidad de que los bienes públicos pudiesen encontrarse en estado "puro". En nuestra tesis exponemos, con el ejemplo del FLOSS (Free/Libre Open Source Software), como la existencia de bienes públicos puros tendría lugar cuando bienes digitales son distribuidos a través de redes "peer to pe...

  20. Quantum dot cascade laser

    OpenAIRE

    Zhuo, Ning; Liu, Feng Qi; Zhang, Jin Chuan; Wang, Li Jun; Liu, Jun Qi; Zhai, Shen Qiang; Wang, Zhan Guo

    2014-01-01

    We demonstrated an unambiguous quantum dot cascade laser based on InGaAs/GaAs/InAs/InAlAs heterostructure by making use of self-assembled quantum dots in the Stranski-Krastanow growth mode and two-step strain compensation active region design. The prototype generates stimulated emission at λ ~ 6.15 μm and a broad electroluminescence band with full width at half maximum over 3 μm. The characteristic temperature for the threshold current density within the temperature range of 82 to 162 K is up...

  1. 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

  2. Analysis of Cl center dot center dot center dot Cl and C-H center dot center dot center dot Cl intermolecular interactions involving chlorine in substituted 2-chloroquinoline derivatives

    OpenAIRE

    Hathwar, Venkatesha R.; Roopan, Mohana S; R. Subashini; Khan, Nawaz F; Row, Guru TN

    2010-01-01

    Six crystal structures of substituted 2-chloroquinoline derivatives have been analysed to evaluate the role of Cl atom as a self recognizing unit resulting in the formation of Cl center dot center dot center dot Cl and C-H center dot center dot center dot Cl interactions to generate supramolecular assembly in the solid state. The features of Type I and Type II geometries associated with Cl center dot center dot center dot Cl interactions have been analysed to show directional preferences lead...

  3. 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.

  4. 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...

  5. Colloidal Double Quantum Dots

    Science.gov (United States)

    2016-01-01

    Conspectus 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

  6. 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

  7. 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...

  8. 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 ...

  9. 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 ...

  10. 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...

  11. 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...

  12. 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.

  13. 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.

  14. 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...

  15. Quantum dots in graphene

    OpenAIRE

    Silvestrov, P.G.; Efetov, K. B.

    2006-01-01

    We suggest a way of confining quasiparticles by an external potential in a small region of a graphene strip. Transversal electron motion plays a crucial role in this confinement. Properties of thus obtained graphene quantum dots are investigated theoretically for different types of the boundary conditions at the edges of the strip. The (quasi)bound states exist in all systems considered. At the same time, the dependence of the conductance on the gate voltage carries an information about the s...

  16. 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.

  17. Quantum dot solar cell

    International Nuclear Information System (INIS)

    Full text: The much awaited desire of replacing fossil fuel with photovoltaic will remain a fairy tale if the myriad of issues facing solar cell development are marginalized. Foremost in the list is the issue of cost. Silicon has reached a stage where its use on large scale can no longer be lavishly depended upon. The demand for high grade silicon from the microelectronics and solar industries has soared leading to scarcity. New approach has to be sought. Notable is the increased attention on thin films such as cadmium telluride, copper indium gallium diselenide, amorphous silicon, and the not so thin non-crystalline family of silicon. While efforts to address the issues of stability, toxicity and efficiency of these systems are ongoing, another novel approach is quietly making its appearance - quantum dots. Quantum dots seem to be promising candidates for solar cells because of the opportunity to manipulate their energy levels allowing absorption of a wider solar spectrum. Utilization of minute quantity of these nano structures is enough to bring the cost of solar cell down and to ascertain sustainable supply of useful material. The paper outlines the progress that has been made on quantum dot solar cells. (author)

  18. 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.

  19. From single dots to interacting arrays

    OpenAIRE

    Gudmundsson, Vidar; Manolescu, Andrei; Krahne, Roman; Heitmann, Detlef

    2001-01-01

    We explore the structural changes in charge the density and the electron configuration of quantum dots caused by the presence of other dots in an array, and the interaction of neighboring dots. We discuss what recent measurements and calculation of the far-infrared absorption reveal about almost isolated quantum dots and investigate some aspects of the complex transition from isolated dots to dots with strongly overlapping electron density. We also address the the effects on the magnetization...

  20. 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...

  1. 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...

  2. Étude comparative de substances bioactives pour la protection des biens patrimoniaux contre les insectes ravageurs

    OpenAIRE

    Nicosia, Grazia; Fohrer, Fabien; Dechezleprêtre, Yoanna; Billerbeck, Virginia Gisel de

    2013-01-01

    Certaines collections patrimoniales sont infestées de manière cyclique par les insectes ravageurs. Les traitements curatifs utilisés sont des opérations ponctuelles d'éradication et ne règlent en aucune manière les ré-infestations chroniques des biens culturels sensibles. Certains produits répulsifs sont pour cela utilisés de manière préventive. Or la plupart s'avèrent dangereux pour l’homme et nombre d'entre eux sont en passe d’être interdits par la réglementation européenne et sa transcript...

  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. Transport and bioaccumulation of polychlorinated dibenzo-p-dioxins and dibenzofurans at the Bien Hoa Agent Orange hotspot in Vietnam.

    Science.gov (United States)

    Van Thuong, Nguyen; Hung, Nguyen Xuan; Mo, Nguyen Thi; Thang, Nguyen Manh; Huy, Pham Quang; Van Binh, Hoang; Nam, Vu Duc; Van Thuy, Nguyen; Son, Le Ke; Minh, Nguyen Hung

    2015-10-01

    The Bien Hoa airbase (south of Vietnam) is known as one of the Agent Orange hotspots which have been seriously contaminated by Agent Orange/dioxin during the Vietnam War. Hundreds of samples including soil, sediment and fish were collected at the Bien Hoa Agent Orange hotspot for assessment of the environmental contamination caused by dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs). The toxicity equivalency quotient (TEQ) concentration of PCDD/Fs in soil and sediment varied from 7.6 to 962,000 and 17 to 4860 pg/g dry wt, respectively, implying very high contamination of PCDD/Fs in several areas. PCDD/F levels in fish ranged between 1.8 and 288 pg/g TEQ wet wt and was generally higher than advisory guidelines for food consumption. 2,3,7,8-Tetrachlorinated dibenzo-p-dioxins (2,3,7,8-TCDD) contributed 66-99 % of TEQ for most of the samples, suggesting 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) from Agent Orange as the major source of the contamination. The vertical transport of PCDD/Fs was observed in soil column with high TEQ levels above 1000 pg/g dry wt (Vietnamese limit for necessary remediation activities- TCVN 8183:2009 (2009)) even at a depth of 1.8 m. The vertical transport of PCDD/Fs has probably mainly taken place during the "Ranch Hand" defoliant spray activities due to the leaks and spills of phenoxy herbicides and solvents. The congener patterns suggest that transports of PCDD/Fs by weathering processes have led to their redistribution in the low-land areas. Also, an estimate for the total volume of contaminated soil requiring remediation to meet Vietnamese regulatory limits is provided. PMID:25510612

  5. Electrochromic nanocrystal quantum dots.

    Science.gov (United States)

    Wang, C; Shim, M; Guyot-Sionnest, P

    2001-03-23

    Incorporating nanocrystals into future electronic or optoelectronic devices will require a means of controlling charge-injection processes and an understanding of how the injected charges affect the properties of nanocrystals. We show that the optical properties of colloidal semiconductor nanocrystal quantum dots can be tuned by an electrochemical potential. The injection of electrons into the quantum-confined states of the nanocrystal leads to an electrochromic response, including a strong, size-tunable, midinfrared absorption corresponding to an intraband transition, a bleach of the visible interband exciton transitions, and a quench of the narrow band-edge photoluminescence. PMID:11264530

  6. La location de l'usage : une interprétation écoresponsable du service ? : cas des biens en partage

    OpenAIRE

    Carry, Dominique,

    2013-01-01

    Des offres de location de biens en partage fleurissent dans les villes : Vélib’, Autolib’, l’autopartage.... Louer l’usage suppose de partager l’utilisation du bien à plusieurs et d’accepter de se dégager de la matérialité au profit de la fonctionnalité. C’est aussi un argument en faveur d’une consommation plus écoresponsable. Louer l’usage d’un bien en partage ou l’acheter, qu’en pense le consommateur ? La valeur réside dans les bénéfices qu'il retire de l’utilisation, et non de la possessio...

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

    OpenAIRE

    Clara In��s Atehortúa-Arredondo

    2010-01-01

    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 ...

  8. Printer model for dot-on-dot halftone screens

    Science.gov (United States)

    Balasubramanian, Raja

    1995-04-01

    A printer model is described for dot-on-dot halftone screens. For a given input CMYK signal, the model predicts the resulting spectral reflectance of the printed patch. The model is derived in two steps. First, the C, M, Y, K dot growth functions are determined which relate the input digital value to the actual dot area coverages of the colorants. Next, the reflectance of a patch is predicted as a weighted combination of the reflectances of the four solid C, M, Y, K patches and their various overlays. This approach is analogous to the Neugebauer model, with the random mixing equations being replaced by dot-on-dot mixing equations. A Yule-Neilsen correction factor is incorporated to account for light scattering within the paper. The dot area functions and Yule-Neilsen parameter are chosen to optimize the fit to a set of training data. The model is also extended to a cellular framework, requiring additional measurements. The model is tested with a four color xerographic printer employing a line-on-line halftone screen. CIE L*a*b* errors are obtained between measurements and model predictions. The Yule-Neilsen factor significantly decreases the model error. Accuracy is also increased with the use of a cellular framework.

  9. Quantum dot cascade laser

    Science.gov (United States)

    2014-01-01

    We demonstrated an unambiguous quantum dot cascade laser based on InGaAs/GaAs/InAs/InAlAs heterostructure by making use of self-assembled quantum dots in the Stranski-Krastanow growth mode and two-step strain compensation active region design. The prototype generates stimulated emission at λ ~ 6.15 μm and a broad electroluminescence band with full width at half maximum over 3 μm. The characteristic temperature for the threshold current density within the temperature range of 82 to 162 K is up to 400 K. Moreover, our materials show the strong perpendicular mid-infrared response at about 1,900 cm-1. These results are very promising for extending the present laser concept to terahertz quantum cascade laser, which would lead to room temperature operation. PACS 42.55.Px; 78.55.Cr; 78.67.Hc PMID:24666965

  10. La Obra Bien Hecha para la mejora docente: un enfoque práctico en el Módulo Repoblaciones Forestales y Tratamientos Selvícolas

    OpenAIRE

    Ramírez-Valiente, María

    2015-01-01

    La ejecución de las diferentes actividades y prácticas que se realizan en los Ciclos Formativos han de contribuir a la cualificación profesional del alumnado que los cursa. Se entiende que sería mucho más efectiva desde la Obra Bien Hecha y la personalización educativa de dichos Ciclos. A partir de lo cual, el objetivo general del TFM es abordar de forma teórica-práctica la Obra Bien Hecha en el Módulo de Repoblaciones Forestales y Tratamientos Selvícolas (RFTS ) del Ciclo Formativo de Grado ...

  11. 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...

  12. Gasto particularista en bienes públicos locales: índice de desviación Particularistic expenditure on local public goods: an index of deviation

    OpenAIRE

    María Alejandra Armesto

    2012-01-01

    El gasto particularista del gobierno se opone al gasto programático. Los dos tipos de medidas clasifican los beneficios de políticas como particularistas si son bienes exclusivos o si son explicados por variables políticas. Este artículo desarrolla un índice de gasto particularista en bienes públicos locales medido como desviación con respecto al programa. Se aplica el índice a la oferta de servicios básicos por administraciones subnacionales seleccionadas en México y Argentina. Se muestra qu...

  13. Una aproximación a los factores claves para la gestión de los bienes de patrimonio cultural

    OpenAIRE

    Fresneda Fuentes, Silvia; Lobo Gallardo, Antonio

    2014-01-01

    El turismo cultural está basado en la gestión y explotación, entre otros, de los bienes catalogados como patrimonio cultural. La necesidad de obtener resultados positivos ha generado una preocupación creciente por identificar los factores clave de éxito. El principal objetivo de este trabajo ha sido la identificación de los mismos, para lo que se ha realizado una revisión bibliográfica. Entendemos que la gestión de estos bienes se debe abordar de la lógica de la mejora continua y una perspect...

  14. Competitividad de la industria de bienes de equipo de España y Alemania (1993-2008): ventaja absoluta y costes relativos

    OpenAIRE

    Boundi Chraki, Fahd

    2014-01-01

    El presente trabajo realizará un análisis comparativo del sector de bienes de equipo de España y Alemania, con el objeto de desentrañar los determinantes de la competitividad de esta industria. La hipótesis central es la siguiente: la industria de bienes de equipo de Alemania es más competitiva debido a su mayor productividad real y sus menores costes relativos. De este modo, se partirá de la teoría clásica y marxiana de la formación de los precios, y el modelo de las ventajas absolutas de An...

  15. 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 ...

  16. 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 ...

  17. ANALYTICAL REVIEW FOR DIFFERENT ASPECTS OF DOT GAIN

    OpenAIRE

    Parag Dnyandeo Nathe

    2013-01-01

    This document gives information about Dot reproduction, Dot gain, factors affecting dot gain, calculation of dot gain measurement and control over dot gain in different controlling parameters. Dot generation in print reproduction and different aspects which causes dot gain during image generation with photochemical process, during printing with mechanical process and during visual inspection of print dot gain is occurred. This document gives information about all causes of dot gain and contr...

  18. 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...

  19. 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...

  20. 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.

  1. Semiconductor nanocrystals inside spherical microcavities: A case of quantum dots in photonic dots

    OpenAIRE

    Artemyev, M. V.

    2003-01-01

    Quantum dots in photonic dots, a new type of microstructures involving highly luminescent II-VI semiconductor nanocrystals has been proposed and realized by incorporating nanocrystals (quantum dots) into glass and polymeric microspheres. The high quality micron-size microspheres represent simplest fully three-dimensional microcavities (photonic dots). Coupling of discrete electron states of quantum dots and photon states inside photonic dots strongly affects onto both stationary and dynamic p...

  2. 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.

  3. DOT Official County Highway Map

    Data.gov (United States)

    Minnesota Department of Natural Resources — The County Highway Map theme is a scanned and rectified version of the original MnDOT County Highway Map Series. The cultural features on some of these maps may be...

  4. 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...

  5. 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...

  6. 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.

  7. Scalable Quantum Computing with "Enhancement" Quantum Dots

    CERN Document Server

    Lyanda-Geller, Y B; Yang, M J

    2005-01-01

    We propose a novel scheme of solid state realization of a quantum computer based on single spin "enhancement mode" quantum dots as building blocks. In the enhancement quantum dots, just one electron can be brought into initially empty dot, in contrast to depletion mode dots based on expelling of electrons from multi-electron dots by gates. The quantum computer architectures based on depletion dots are confronted by several challenges making scalability difficult. These challenges can be successfully met by the approach based on ehnancement mode, capable of producing square array of dots with versatile functionalities. These functionalities allow transportation of qubits, including teleportation, and error correction based on straightforward one- and two-qubit operations. We describe physical properties and demonstrate experimental characteristics of enhancement quantum dots and single-electron transistors based on InAs/GaSb composite quantum wells. We discuss the materials aspects of quantum dot quantum compu...

  8. 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.

  9. 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.

  10. 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

  11. Prolegómenos al vivir bien-buen vivir: una evaluación normativa y práctica

    Directory of Open Access Journals (Sweden)

    Edwin Cruz Rodríguez

    2015-06-01

    Full Text Available Este trabajo examina el concepto de vivir bien-buen vivir ponderando sus contribuciones y limitaciones. Esta cosmovisión tiene un horizonte normativo más ambicioso que el paradigma del desarrollo, pues apuesta por una concepción de la pobreza y la riqueza que no se reduce a la acumulación de bienes materiales, una economía que comprende sus efectos sobre la naturaleza y se centra en la satisfacción de necesidades, y una descolonización de los saberes. No obstante, se caracteriza por un déficit de operacionalización que se manifiesta en la dificultad para definir políticas concretas e indicadores de medición precisos.

  12. “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.

  13. Ethique de la population : l'apport des critères de bien-être dépendant du rang

    OpenAIRE

    Zuber, Stéphane

    2016-01-01

    Cet article présente l'intérêt que peuvent avoir des critères de bien-être dépendant du rang dans le cadre de l'éthique de la population. Ce champ de recherche s'intéresse à l'évaluation et à la comparaison d'allocations lorsque des populations de tailles différentes sont en jeu. On montre que les critères de bien-être dépendant du rang ne sont pas sujets à plusieurs écueils auxquels sont confrontés les critères utilitaristes (généralisés) habituellement étudiés dans ce champ....

  14. 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...

  15. 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

  16. 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)

    Lilian Delia Curiel Lorenzo

    2010-10-01

    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.

  17. Quantum dot field effect transistors

    Directory of Open Access Journals (Sweden)

    Frederik Hetsch

    2013-09-01

    Full Text Available Solution processed colloidal semiconductor quantum dots offer a high potential for decreasing costs and expanding versatility of many electronic and optoelectronic devices. Initially used as a research tool to study charge carrier mobilities in closely packed quantum dot thin films, field effect transistors with quantum dots as the active layer have recently experienced a breakthrough in performance (achievement of mobilities higher than 30 cm2 V−1 s−1 as a result of a proper choice of surface ligands and/or improved chemical treatment of the nanoparticle films during device processing. Here we review these innovative developments and the continuing work that may soon lead to commercial grade electronic components.

  18. 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.

  19. 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.

  20. 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....

  1. Chaos and Interactions in Quantum Dots

    OpenAIRE

    Alhassid, Y.

    2001-01-01

    Quantum dots are small conducting devices containing up to several thousand electrons. We focus here on closed dots whose single-electron dynamics are mostly chaotic. The mesoscopic fluctuations of the conduction properties of such dots reveal the effects of one-body chaos, quantum coherence and electron-electron interactions.

  2. 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.

  3. 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

  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. 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.

  6. 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.

  7. 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

  8. Quantum dot photonic crystal lasers

    OpenAIRE

    Yoshie, T.; Shchekin, O. B.; Chen, H.; Deppe, D. G.; Scherer, A.

    2002-01-01

    Coupled cavity designs on two-dimensional square lattice photonic crystal slabs were used to demonstrate optically pumped indium arsenide quantum dot photonic crystal lasers at room temperature. Threshold pump powers of 120 and 370 μW were observed for coupled cavities including two and four defect cavities defined in optimised photonic crystals.

  9. 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

  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. 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.

  12. 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.

  13. Estrategias de cumplimentación de pedidos en el sector de fabricación de bienes de equipo. Un estudio empírico

    OpenAIRE

    Sanchis Gisbert, Raquel; Saiz, Eduardo; Castellano, Eduardo; Poler Escoto, Raúl

    2011-01-01

    [ES] : El sector de bienes de equipo se caracteriza por fabricar productos complejos y con un alto grado de personalización. La elección de la estrategia de cumplimentación de pedidos que permita satisfacer de forma eficiente las necesidades específicas de sus clientes se convierte en una decisión estratégica de gran importancia. Como respuesta a esta demanda, el presente estudio analiza la relación entre diferentes estrategias de cumplimentación de pedidos (Ingeniería Bajo Pedido, Fabr...

  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. 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...

  16. AVANCES Y PERSPECTIVAS DEL DERECHO PARA LA RESTITUCIÓN DE BIENES CULTURALES A SUS PAÍSES DE ORIGEN EL CASO DEL PATRIMONIO CULTURAL

    OpenAIRE

    Antonio José Rengifo Lozano

    2008-01-01

    El debate sobre la restitución de bienes del patrimonio cultural, como una forma de reivindicación por coparte de los países de origen, se ha ido incrementando en la escena internacional y en el derecho publico, a favor de los procesos de constitucionalizacion de la cultura en el mundo, como ha sido el caso de la constitución política de Colombia de 1.991 de la adopción de tratados internacionales y del rol eficaz del comité intergubernamental de la UNESCO, como organismo internacional instit...

  17. Avances y perspectivas del derecho para la restitución de bienes culturales a sus países de origen: el caso del patrimonio cultural quimbaya

    OpenAIRE

    Rengifo Lozano, Antonio José

    2013-01-01

    Con base en el estudio comparado de los casos de restitución de los Mármoles del Partenón, promovido por Grecia y del Patrimonio Cultural Quimbaya en Colombia, el presente artículo sustenta la tesis de que aunque el derecho para la restitución de bienes culturales se encuentra en etapa inicial de consolidación y, por tanto, de seguro tendrá muchos desarrollos en el futuro, existen en la actualidad bases jurídicas suficientes para hacer efectiva esa restitución, necesaria para realizar el l...

  18. 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...

  19. 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...

  20. 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...

  1. La respuesta a la vocación al bien común de las empresas cotizadas en la bolsa mexicana de valores

    OpenAIRE

    Reyes-Sahagun, C. A. (Carlos Antonio); Dembinski, P. (Paul)

    2016-01-01

    Las decisiones en la empresa moderna tienen influencia de ideas académicas que ponen énfasis en la máxima eficiencia para generar beneficios económicos en favor del accionista y en los acuerdos contractuales entre las diversas partes interesadas. En esta tesis se investiga cómo estos dos aspectos pueden enriquecerse con el estudio del concepto de bien común de la tradición aristotélico-tomista y de la Doctrina Social de la Iglesia. Estas ideas proporcionan una visión más amplia...

  2. 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...

  3. Dot-in-Well Quantum-Dot Infrared Photodetectors

    Science.gov (United States)

    Gunapala, Sarath; Bandara, Sumith; Ting, David; Hill, cory; Liu, John; Mumolo, Jason; Chang, Yia Chung

    2008-01-01

    Dot-in-well (DWELL) quantum-dot infrared photodetectors (QDIPs) [DWELL-QDIPs] are subjects of research as potentially superior alternatives to prior QDIPs. Heretofore, there has not existed a reliable method for fabricating quantum dots (QDs) having precise, repeatable dimensions. This lack has constituted an obstacle to the development of uniform, high-performance, wavelength-tailorable QDIPs and of focal-plane arrays (FPAs) of such QDIPs. However, techniques for fabricating quantum-well infrared photodetectors (QWIPs) having multiple-quantum- well (MQW) structures are now well established. In the present research on DWELL-QDIPs, the arts of fabrication of QDs and QWIPs are combined with a view toward overcoming the deficiencies of prior QDIPs. The longer-term goal is to develop focal-plane arrays of radiationhard, highly uniform arrays of QDIPs that would exhibit high performance at wavelengths from 8 to 15 m when operated at temperatures between 150 and 200 K. Increasing quantum efficiency is the key to the development of competitive QDIP-based FPAs. Quantum efficiency can be increased by increasing the density of QDs and by enhancing infrared absorption in QD-containing material. QDIPs demonstrated thus far have consisted, variously, of InAs islands on GaAs or InAs islands in InGaAs/GaAs wells. These QDIPs have exhibited low quantum efficiencies because the numbers of QD layers (and, hence, the areal densities of QDs) have been small typically five layers in each QDIP. The number of QD layers in such a device must be thus limited to prevent the aggregation of strain in the InAs/InGaAs/GaAs non-lattice- matched material system. The approach being followed in the DWELL-QDIP research is to embed In- GaAs QDs in GaAs/AlGaAs multi-quantum- well (MQW) structures (see figure). This material system can accommodate a large number of QD layers without excessive lattice-mismatch strain and the associated degradation of photodetection properties. Hence, this material

  4. Adiabatic pumping through quantum dots

    International Nuclear Information System (INIS)

    A finite charge can be pumped through a mesoscopic system in the absence of an applied bias voltage by changing periodically in time some parameters of the system. If these parameters change slowly with respect to all internal time scales of the system, pumping is adiabatic. The scope of this work is to investigate adiabatic pumping through a quantum dot, in particular the influence of Coulomb interaction between electrons in the dot on the pumped charge. On one hand we develop a formalism based on Green's functions, in order to calculate the pumped charge from the weak-tunnel-coupling regime down to the Kondo regime. We extend our calculations to a system with a superconducting contact. On the other hand we use a systematic perturbation expansion for the calculation of the pumped charge, giving us the possibility to analyze processes which contribute to charge pumping and to highlight the important role of interaction-induced level renormalization. (orig.)

  5. Quantum dots: promises and accomplishments

    Directory of Open Access Journals (Sweden)

    Dieter Bimberg

    2011-09-01

    Full Text Available Exploration of the Stranski-Krastanow growth of strained semiconductor heterostructures marked the major breakthrough for easy fabrication of defect-free quantum dots (QDs. For the first time, single QDs are facilitating the development of electrically operated emitters of single polarized or entangled photons on demand: an essential component for quantum communication systems. QDs inserted in quantum wells, stacked in planes upon each other, have led to semiconductor lasers that can operate at wavelengths that were previously impossible, or at least difficult to reach, for a given semiconductor family. These lasers show excellent temperature stability, large radiation resistance, and excellent temporal and spatial stability. In this review we discuss recent progress in the field of quantum dot devices.

  6. Charging graphene nanoribbon quantum dots

    OpenAIRE

    Żebrowski, D. P.; B. Szafran

    2015-01-01

    We describe charging a quantum dot induced electrostatically within a semiconducting graphene nanoribbon by electrons or holes. The applied model is based on a tight-binding approach with the electron-electron interaction introduced by a mean field local spin density approximation. The numerical approach accounts for the charge of all the $p_z$ electrons and screening of external potentials by states near the charge neutrality point. Both a homogenous ribbon and a graphene flake embedded with...

  7. FRET sensor with quantum dot

    Czech Academy of Sciences Publication Activity Database

    Datinská, Vladimíra; Klepárník, Karel; Belšánová, Barbora; Minárik, M.; Foret, František

    Veszprém: PANNON Egyetem, 2015 - (Mizsey, P.), s. 20-23 ISBN 978-963-396-072-1. [Műszaki Kémiai Napok 2015. Veszprém (HU), 21.04.2015-23.04.2015] R&D Projects: GA ČR(CZ) GA14-28254S; GA TA ČR(CZ) TA02010672 Institutional support: RVO:68081715 Keywords : FRET * quantum dot * sensor Subject RIV: CB - Analytical Chemistry, Separation

  8. FRET sensor with quantum dot

    Czech Academy of Sciences Publication Activity Database

    Datinská, Vladimíra; Klepárník, Karel; Belšánová, Barbora; Minárik, M.; Foret, František

    Veszprém : PANNON Egyetem, 2015 - (Mizsey, P.), s. 20-23 ISBN 978-963-396-072-1. [Műszaki Kémiai Napok 2015. Veszprém (HU), 21.04.2015-23.04.2015] R&D Projects: GA ČR(CZ) GA14-28254S; GA TA ČR(CZ) TA02010672 Institutional support: RVO:68081715 Keywords : FRET * quantum dot * sensor Subject RIV: CB - Analytical Chemistry, Separation

  9. Semiconductor quantum-dot lasers and amplifiers

    DEFF Research Database (Denmark)

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

    2002-01-01

    We have produced GaAs-based quantum-dot edge-emitting lasers operating at 1.16 mu m with record-low transparency current, high output power, and high internal quantum efficiencies. We have also realized GaAs-based quantum-dot lasers emitting at 1.3 mu m, both high-power edge emitters and low-power...... 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...... 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...

  10. Ultrasmall colloidal PbS quantum dots

    International Nuclear Information System (INIS)

    Ultrasmall colloidal lead sulfide quantum dots can increase the open circuit voltages of quantum-dot-based solar cells because of their large energy gap. Their small size and visible or near infrared light-emitting property make them attractive to the applications of biological fluorescence labeling. Through a modified organometallic route, we can synthesize lead sulfide quantum dots as small as 1.6 nm in diameter. The low reaction temperature and the addition of a chloroalkane cosolvent decrease the reaction rate, making it possible to obtain the ultrasmall quantum dots. - Highlights: • Ultrasmall colloidal PbS quantum dots as small as 1.6 nm in diameter are synthesized. • The quantum dots emit red light with photoluminescence peak at 760 nm. • The growth temperature is as low as 50 °C. • Addition of cosolvent 1,2-dichloroethane in the reaction decreases the reaction rate

  11. 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)

  12. 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.

  13. 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...

  14. 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.

  15. Spintronics and Quantum Computing with Quantum Dots

    OpenAIRE

    Recher, P.; Loss, D.; Levy, J

    2000-01-01

    The creation, coherent manipulation, and measurement of spins in nanostructures open up completely new possibilities for electronics and information processing, among them quantum computing and quantum communication. We review our theoretical proposal for using electron spins in quantum dots as quantum bits. We present single- and two qubit gate mechanisms in laterally as well as vertically coupled quantum dots and discuss the possibility to couple spins in quantum dots via superexchange. We ...

  16. 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...

  17. 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.

  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

    2009-01-01

    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.

  19. Gasto particularista en bienes públicos locales: índice de desviación Particularistic expenditure on local public goods: an index of deviation

    Directory of Open Access Journals (Sweden)

    María Alejandra Armesto

    2012-09-01

    Full Text Available El gasto particularista del gobierno se opone al gasto programático. Los dos tipos de medidas clasifican los beneficios de políticas como particularistas si son bienes exclusivos o si son explicados por variables políticas. Este artículo desarrolla un índice de gasto particularista en bienes públicos locales medido como desviación con respecto al programa. Se aplica el índice a la oferta de servicios básicos por administraciones subnacionales seleccionadas en México y Argentina. Se muestra que el índice corre menos riesgos de sobreestimar o subestimar el gasto particularista y el gasto programático que las medidas existentes.This article compares particularistic and programmed government spending. The two types of measures classify the benefits of policies as particularistic if they are exclusive goods or if they are determined by political variables. This article contains an index of particularistic expenditure on local public goods, measured as a deviation from the program. It applies this index to the supply of basic services from selected sub-national administrations in Mexico and Argentina. It shows that this index is less likely to over- or under-estimate particularistic and programmatic expenditure than existing measures.

  20. Random Feature Maps for Dot Product Kernels

    CERN Document Server

    Kar, Purushottam

    2012-01-01

    Approximating non-linear kernels using feature maps has gained a lot of interest in recent years due to applications in reducing training and testing times of SVM classifiers and other kernel based learning algorithms. We extend this line of work and present low distortion embeddings for dot product kernels into linear Euclidean spaces. We base our results on a classical result in harmonic analysis characterizing all dot product kernels and use it to define randomized feature maps into explicit low dimensional Euclidean spaces in which the native dot product provides an approximation to the dot product kernel with high confidence.

  1. 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.

  2. Thermoelectric energy harvesting with quantum dots

    International Nuclear Information System (INIS)

    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. (topical review)

  3. L’addiction ou les addictions ; en quête d'un bien-être et pathologie de système ?

    Directory of Open Access Journals (Sweden)

    Thierry Jandrok

    2016-04-01

    Full Text Available Dans le cadre de cet article nous reviendrons sur le sens du terme d’«addiction» qui remplaça, il y a quelques années, celui de «toxicomanie». De nos jours, le discours politiquement correct ne stigmatise plus. Il ne présente plus, n’accuse plus. Il culpabilise et met l'accent sur la fonction consommatrice et la relation d’un individu aux pratiques et aux productions des plaisirs. On parle désormais d'usager, de consommateur. Ce personnage décrit par la vulgate contemporaine est distinctement inclus dans le système marchand des biens et des services. Que cachent ces arguties lexicales ? Quelle est le sens de cette démarche économico-politique qui privilégie la fonction sur le sujet ? Quel est donc ce clivage dans la définition de pratiques qui, bien que collectives, n'en restent pas moins singulières et, par conséquent, inaliénables ? L'addiction n'existe pas sans un référentiel théorique, politique et économique, sans un background à partir duquel certains sens se créent et s'échangent. Dans ce mouvement, l’addiction tend à s’effacer, en même temps que la subjectivité, derrière une brume sémantique qui hésite entre la stigmatisation de pratiques pathologiques singulières et comportements transgressifs, apparemment détachés des échanges. Dans ce cadre, nous interrogerons ces théories qui du semblant et de l’apparence proposent un sens à une fonction au détriment de ceux qui pourraient l’habiter ? Comment le sujet est-il déshabillé de sa consistance, de ses souffrances, de sa jouissance, et finalement de sa quête de bien-être ou de mal-être, au profit de discours qui n’entendent que l’enchaînement des actes comme preuves de qui il serait ? Le retrait de la composante maladive de l’addiction a dénaturé sa réalité. Sans la notion de mal ou le concept de maladie, comment faire valoir le bien et par conséquent redonner sens à la notion de «bien-être» ? Les lumières des discours

  4. 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...

  5. 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

  6. 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.

  7. La opacidad de los acuerdos generales de bienes y servicios en España Opacity of general agreements on goods and services in Spain

    Directory of Open Access Journals (Sweden)

    Román Andrés Umaña Peña

    2006-06-01

    Full Text Available Objetivo: Explorar la intensidad del debate parlamentario sobre el Acuerdo General de Comercio de Servicios (AGCS asumido por España ante la Organización Mundial del Comercio (OMC, y compararla con la del Acuerdo General de Bienes (GATT. Métodos: Búsqueda sistemática y análisis del contenido de todas las iniciativas parlamentarias sobre AGCS y GATT realizadas entre 1979 y 2004 en el Congreso de los Diputados y el Senado. Se calculó la frecuencia y porcentaje de iniciativas parlamentarias de ambos temas, resultado de su tramitación y tipo de iniciativa. Resultados: Se presentaron 185 iniciativas parlamentarias sobre los acuerdos multilaterales de bienes y servicios, de las que 120 se referían al GATT, 8 al AGCS y 57 a ambos acuerdos. La mayoría de las iniciativas no fueron discutidas (GATT, 71%; GATS, 55,4% o estuvieron sujetas a un debate político en el que apenas se dieron intervenciones por parte de los grupos parlamentarios. Conclusiones: A pesar de las implicaciones del acuerdo multilateral de servicios para la política sanitaria española, éste se ha asumido con escaso debate parlamentario previo, incluso menos que en el caso de su homólogo sobre bienes. Se requiere en este tema una intensificación de la función de control al gobierno.Objective: To explore the intensity of the debate in the Spanish Parliament on the General Agreement on Trade in Services (GATS developed by Spain and the World Trade Organization, and to compare it with the debate on the General Agreement on Tariffs and Trade (GATT. Methods: A systematic search and content analysis were performed of all parliamentary initiatives on GATS and GATT undertaken from 1979 to 2004 in the Spanish Parliament and Senate. The frequency and percentages of initiatives on both issues were calculated, and the final result and kinds of initiative were analyzed. Results: A total of 185 initiatives were presented in the Spanish Parliament on these agreements, of which 120 were

  8. 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

  9. 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 ...

  10. 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...... number due to increasing dot size....

  11. 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.

  12. 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.

  13. 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.

  14. Photoluminescence of hybrid quantum dots

    Czech Academy of Sciences Publication Activity Database

    Král, Karel; Menšík, Miroslav

    Bratislava: Slovak Expert Group of Solid State Chemistry and Physics , 2013 - (Koman, M.; Jorík, V.; Kožíšek, Z.). s. 28-28 ISBN 978-80-970896-5-8. [Joint Seminar – Development of materials science in research and education /23./. 09.09.2013-13.09.2013, Kežmarské Žľaby] R&D Projects: GA MŠk LH12236; GA MŠk LH12186 Institutional support: RVO:68378271 ; RVO:61389013 Keywords : energy transfer * quantum dots Subject RIV: BM - Solid Matter Physics ; Magnetism; JA - Electronics ; Optoelectronics, Electrical Engineering (UMCH-V)

  15. Coherent control of quantum dots

    DEFF Research Database (Denmark)

    Johansen, Jeppe; Lodahl, Peter; Hvam, Jørn Märcher

    In recent years much effort has been devoted to the use of semiconductor quantum dotsystems as building blocks for solid-state-based quantum logic devices. One importantparameter for such devices is the coherence time, which determines the number ofpossible quantum operations. From earlier...... measurements the coherence time of the selfassembledquantum dots (QDs) has been reported to be limited by the spontaneousemission rate at cryogenic temperatures1.In this project we propose to alter the coherence time of QDs by taking advantage of arecent technique on modifying spontaneous emission rates with...

  16. Semiconductor double quantum dot micromaser.

    Science.gov (United States)

    Liu, Y-Y; Stehlik, J; Eichler, C; Gullans, M J; Taylor, J M; Petta, J R

    2015-01-16

    The coherent generation of light, from masers to lasers, relies upon the specific structure of the individual emitters that lead to gain. Devices operating as lasers in the few-emitter limit provide opportunities for understanding quantum coherent phenomena, from terahertz sources to quantum communication. Here we demonstrate a maser that is driven by single-electron tunneling events. Semiconductor double quantum dots (DQDs) serve as a gain medium and are placed inside a high-quality factor microwave cavity. We verify maser action by comparing the statistics of the emitted microwave field above and below the maser threshold. PMID:25593187

  17. 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.

  18. Photoluminescence of a quantum-dot molecule

    International Nuclear Information System (INIS)

    The coherent coupling of quantum dots is a sensitive indicator of the energy and phase relaxation processes taking place in the nanostructure components. We formulate a theory of low-temperature, stationary photoluminescence from a quantum-dot molecule composed of two spherical quantum dots whose electronic subsystems are resonantly coupled via the Coulomb interaction. We show that the coupling leads to the hybridization of the first excited states of the quantum dots, manifesting itself as a pair of photoluminescence peaks with intensities and spectral positions strongly dependent on the geometric, material, and relaxation parameters of the quantum-dot molecule. These parameters are explicitly contained in the analytical expression for the photoluminescence differential cross section derived in the paper. The developed theory and expression obtained are essential in interpreting and analyzing spectroscopic data on the secondary emission of coherently coupled quantum systems

  19. L’évocation des biens communs dans les revendications citoyennes contre le gaz de schiste au Québec

    OpenAIRE

    Goupil, Sylvie

    2016-01-01

    Le présent article s’interroge sur l’action citoyenne et plus particulièrement sur ce qui peut pousser des personnes, qui ont toujours vécu dans un « anonymat politique », à se lancer dans une action publique qui interpelle les gouvernements. L’auteure prend pour point de départ la conception selon laquelle des préoccupations vécues dans la vie quotidienne sont à l’origine d’une prise de conscience quant à un problème qui concerne ce que les acteurs identifient comme des biens communs. Elle i...

  20. Les représentations de l’animal et du bien-être animal par les éleveurs français

    OpenAIRE

    Dockes, Anne-Charlotte; Kling-Eveillard, Florence

    2007-01-01

    Plusieurs travaux récents ont permis d’appréhender les représentations des éleveurs, vis-à-vis de l’animal et du bien-être animal. Ils mettent en évidence un certain nombre d’éléments communs à tous les éleveurs : la place centrale de l’animal dans la définition du métier, la relation professionnelle aux animaux, le rôle central de l’observation dans le métier d’éleveur… Ils montrent la diversité des représentations de l’élevage, des animaux d’élevage et des pratiques, en fonction du type d’a...

  1. Les caractéristiques du climat forestier et son influence sur le bien-être: le cas de l'été 2003 en Suisse

    OpenAIRE

    Läderach, Sabina; Rebetez, Martine

    2007-01-01

    Les dernières décennies ont été caractérisées par le dépassement régulier du record des périodes les plus chaudes depuis le début de l’enregistrement des mesures météorologiques et il devient de plus en plus clair que nous devrons apprendre à faire face à des situations de canicule de plus en plus fréquentes. Est-ce que la forêt peut jouer un rôle favorable pour notre bien-être dans ce contexte? L’enjeu de ce mémoire est de répondre à cette question. Cela dans un premier temps en comparant le...

  2. 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.

  3. 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...

  4. Silicon quantum dots: surface matters

    International Nuclear Information System (INIS)

    Silicon quantum dots (SiQDs) hold great promise for many future technologies. Silicon is already at the core of photovoltaics and microelectronics, and SiQDs are capable of efficient light emission and amplification. This is crucial for the development of the next technological frontiers—silicon photonics and optoelectronics. Unlike any other quantum dots (QDs), SiQDs are made of non-toxic and abundant material, offering one of the spectrally broadest emission tunabilities accessible with semiconductor QDs and allowing for tailored radiative rates over many orders of magnitude. This extraordinary flexibility of optical properties is achieved via a combination of the spatial confinement of carriers and the strong influence of surface chemistry. The complex physics of this material, which is still being unraveled, leads to new effects, opening up new opportunities for applications. In this review we summarize the latest progress in this fascinating research field, with special attention given to surface-induced effects, such as the emergence of direct bandgap transitions, and collective effects in densely packed QDs, such as space separated quantum cutting. (topical review)

  5. ¿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...

  6. 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.

  7. Magnon-driven quantum dot refrigerators

    Science.gov (United States)

    Wang, Yuan; Huang, Chuankun; Liao, Tianjun; Chen, Jincan

    2015-12-01

    A new model of refrigerator consisting of a spin-splitting quantum dot coupled with two ferromagnetic reservoirs and a ferromagnetic insulator is proposed. The rate equation is used to calculate the occupation probabilities of the quantum dot. The expressions of the electron and magnon currents are obtained. The region that the system can work in as a refrigerator is determined. The cooling power and coefficient of performance (COP) of the refrigerator are derived. The influences of the magnetic field, applied voltage, and polarization of two leads on the performance are discussed. The performances of two different magnon-driven quantum dot refrigerators are compared.

  8. Introduction to the physics of quantum dots

    International Nuclear Information System (INIS)

    Quantum dots contain only a few well-defined energy levels for electron and/or holes as a result of the confinement of charge in all three spatial dimensions. Here, we describe both the application of photoluminescence spectroscopy and transport measurements to the characterisation of quantum dots and the novel phenomena that they exhibit. These include the Coulomb blockade, single electron tunneling and single photon detection. The impact of quantum dots on future electronics and directions for future research, such as in quantum computing and cryptography, are discussed. (author)

  9. Nonuniform magnetization reversals in elliptical permalloy dots

    Energy Technology Data Exchange (ETDEWEB)

    Lai, M.-F.; Wei, Z.-H. E-mail: zhwei@phys.ntu.edu.tw; Chang, Ching-Ray; Usov, N.A.; Wu, J.C.; Lai, Jun-Yang

    2004-11-01

    Reversible and irreversible magnetization processes of the single-domain elliptical permalloy dot are studied by simulation. The magnetization curve of the reversible process obtained by applying the field along the hard axis of the elliptical dot is almost linear, as is the case in the single-domain ellipsoidal particle. Due to the occurrence of the non uniform reversal, the switching field is reduced significantly compared to that predicted by the Stoner-Wohlfarth model. The nucleation fields of elliptical dots are calculated as a function of ellipse's aspect ratio, and the function reveals a step-like behavior.

  10. Structural and optical characterization of Si/Ge quantum dots

    OpenAIRE

    Wigblad, Dan

    2008-01-01

    In this study silicon-germanium quantum dots grown on silicon have been investigated. The aim of the work was to find quantum dots suitable for use as a thermistor material. The quantum dots were produced at KTH, Stockholm, using a RPCVD reactor that is designed for industrial production. The techniques used to study the quantum dots were: HRSEM, AFM, HRXRD, FTPL, and Raman spectroscopy. Quantum dots have been produced in single and multilayer structures. As a result of this work a multilayer...

  11. Quantum dot devices for optical communications

    DEFF Research Database (Denmark)

    Mørk, Jesper

    2005-01-01

    record-low threshold currents and amplifiers with record-high power levels. In this tutorial we will review the basic properties of quantum dots, emphasizing the properties which are important for laser and amplifier applications, as well as devices for all-optical signal processing. The high....... The main property of semiconductor quantum dots compared to bulk material or even quantum well structures is the discrete nature of the allowed states, which means that inversion of the medium can be obtained for very low electron densities. This has led to the fabrication of quantum dot lasers with......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...

  12. 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...

  13. 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...

  14. Quantum Phase Transitions in Quantum Dots

    OpenAIRE

    Rau, I. G.; Amasha, S.; Oreg, Y.; Goldhaber-Gordon, D.

    2013-01-01

    This review article describes theoretical and experimental advances in using quantum dots as a system for studying impurity quantum phase transitions and the non-Fermi liquid behavior at the quantum critical point.

  15. 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

  16. 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

  17. 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

  18. 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.

  19. Quantum dot cascade laser: Arguments in favor

    OpenAIRE

    Dmitriev, I. A.; Suris, R. A.

    2007-01-01

    Quantum cascade lasers are recognized as propitious candidates for future terahertz optoelectronics. Here we demonstrate several definite advantages of quantum dot cascade structures over quantum well devices, which suffer fundamental performance limitations owing to continuous carrier spectrum. The discrete spectrum of quantum dots opens an opportunity to control the non-radiative relaxation and optical loss and also provides for more flexibility in the choice of an optical and electrical de...

  20. Electronic Commerce Beyond the "dot com" Boom

    OpenAIRE

    James A. Senn

    2000-01-01

    The explosion of interest in electronic commerce stemming from commercial use of the Internet triggered high expectations, and accompanying high stock market value for public companies specializing in the delivery of products and services through this channel. However, the boom in the market value of these so-called "dot com" companies appears to be over. This paper examines the factors underlying the fall off in the value of "dot com" companies, focusing on the manner in which fundamental bu...

  1. Positioning of quantum dots on metallic nanostructures

    International Nuclear Information System (INIS)

    The capability to position individual emitters, such as quantum dots, near metallic nanostructures is highly desirable for constructing active optical devices that can manipulate light at the single photon level. The emergence of the field of plasmonics as a means to confine light now introduces a need for high precision and reliability in positioning any source of emission, which has thus far been elusive. Placing an emission source within the influence of plasmonic structures now requires accuracy approaching molecular length scales. In this paper we report the ability to reliably position nanoscale functional objects, specifically quantum dots, with sub-100-nm accuracy, which is several times smaller than the diffraction limit of a quantum dot's emission light. Electron beam lithography-defined masks on metallic surfaces and a series of surface chemical functionalization processes allow the programmed assembly of DNA-linked colloidal quantum dots. The quantum dots are successfully functionalized to areas as small as (100 nm)2 using the specific binding of thiolated DNA to Au/Ag, and exploiting the streptavidin-biotin interaction. An analysis of the reproducibility of the process for various pattern sizes shows that this technique is potentially scalable to the single quantum dot level with 50 nm accuracy accompanied by a moderate reduction in yield.

  2. 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).

  3. 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.

  4. 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

  5. Coherent transport through interacting quantum dots

    International Nuclear Information System (INIS)

    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

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. (In,Mn)As multilayer quantum dot structures

    International Nuclear Information System (INIS)

    (In,Mn)As multilayer quantum dots structures were grown by molecular beam epitaxy using a Mn selective doping of the central parts of quantum dots. The study of the structural and magneto-optical properties of the samples with three and five layers of (In,Mn)As quantum dots has shown that during the quantum dots assembly, the out-diffusion of Mn from the layers with (In,Mn)As quantum dots can occur resulting in the formation of the extended defects. To produce a high quality structures using the elaborated technique of selective doping, the number of (In,Mn)As quantum dot layers should not exceed three

  11. 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.

  12. Non-Equilibrium Electron Transport through a Double Quantum Dot System: Study of Two Exchange Coupled Quantum Dots in a 4-Terminal Geometry

    OpenAIRE

    Koerting, Verena

    2007-01-01

    In this thesis we study two exchange-coupled quantum dots with an emphasis on non-equilibrium physics. Assuming a single electron on each quantum dot, the double quantum dot system is characterized by an interplay between the Kondo spin coupling of the dots with the leads and the spin-exchange coupling between the dots. We find that a finite voltage on one quantum dot drives the other quantum dot out of equilibrium.

  13. 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

  14. 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)

  15. 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.

  16. 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.

  17. 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.

  18. Quantum dot optoelectronic devices: lasers, photodetectors and solar cells

    International Nuclear Information System (INIS)

    Nanometre-scale semiconductor devices have been envisioned as next-generation technologies with high integration and functionality. Quantum dots, or the so-called ‘artificial atoms’, exhibit unique properties due to their quantum confinement in all 3D. These unique properties have brought to light the great potential of quantum dots in optoelectronic applications. Numerous efforts worldwide have been devoted to these promising nanomaterials for next-generation optoelectronic devices, such as lasers, photodetectors, amplifiers, and solar cells, with the emphasis on improving performance and functionality. Through the development in optoelectronic devices based on quantum dots over the last two decades, quantum dot devices with exceptional performance surpassing previous devices are evidenced. This review describes recent developments in quantum dot optoelectronic devices over the last few years. The paper will highlight the major progress made in 1.3 μm quantum dot lasers, quantum dot infrared photodetectors, and quantum dot solar cells. (topical review)

  19. 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.

  20. Few-quantum-dot lasing in photonic crystal nanocavities

    DEFF Research Database (Denmark)

    Liu, Jin; Ates, Serkan; Stobbe, Søren; Lorke, Michael; Lodahl, Peter

    2012-01-01

    A very smooth lasing transition in photonic crystal nanocavities with embedded quantum dots is observed and compared to the theory. Decay rate measurements reveal that only a few quantum dots are feeding the cavity.......A very smooth lasing transition in photonic crystal nanocavities with embedded quantum dots is observed and compared to the theory. Decay rate measurements reveal that only a few quantum dots are feeding the cavity....

  1. Luminescence Spectra of a Quantum-Dot Cascade Laser

    OpenAIRE

    Apalkov, Vadim; Chakraborty, Tapash

    2000-01-01

    A quantum cascade laser where the quantum wells in the active regions are replaced by quantum dots with their atom-like discrete energy levels is an interesting system to study novel features in optical spectroscopy. We study structures suitable for diagonal lasing transitions in coupled dots, and vertical lasing transitions in a single dot, in the active regions of the laser device. The luminescence spectra as a function of electron number and dot size show that for diagonal transitions, a s...

  2. 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...

  3. Optical properties of a Quantum-Dot Cascade Structure

    OpenAIRE

    Apalkov, V. M.; Chakraborty, Tapash

    2001-01-01

    We report on our theoretical studies of the luminescence spectra of a quantum cascade laser where the quantum wells in the active regions are replaced by parabolic quantum dots. We analyze the influence of shape and size of the dots on the luminescence spectra. The emission spectra have interaction induced blueshift which increases almost linearly with increasing electron number. The blueshift is smaller for larger and non-circular dots. For large dots, shape of the emission line has weak dep...

  4. Excitonic Properties in GaAs Parabolic Quantum Dots

    OpenAIRE

    Jaziri, S.; Bennaceur, R.

    1995-01-01

    Certain classes of semiconductor quantum dots being actually fabricated exhibit a nearly parabolic confinement for both the electron and the hole. In undoped quantum dots, excitonic effects are important. In this work, first we present theoretical results on exciton properties in parabolic quantum dots: resonance energy, binding energy and oscillator strength. Then, we investigate the effects of external electric and magnetic fields on exciton in quantum dots.

  5. 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.

  6. 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.

  7. 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.

  8. 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 (cotunneli...

  9. Weak localization in arrays of metallic quantum dots

    OpenAIRE

    Golubev, Dmitri S.; Zaikin, Andrei D.

    2006-01-01

    Combining scattering matrix formalism with non-linear $\\sigma$-model technique we analyze weak localization effects in arrays of chaotic quantum dots connected via barriers with arbitrary distribution of channel transmissions. With the aid of our approach we evaluate magnetoconductance of two arbitrarily connected quantum dots as well as of $N\\times M$ arrays of identical quantum dots.

  10. 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

  11. 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.

  12. 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...

  13. Nonuniform micromagnetic states in thin circular dots

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Z.-H. E-mail: zhwei@phys.ntu.edu.tw; Lai, M.-F.; Chang, C.-R.; Usov, N.A.; Wu, J.C.; Lai, J.-Y

    2004-11-01

    Micromagnetic states are strongly related to sizes of nano-dots. The quasiuniform state becomes unstable and transforms to a new nonuniform state as the diameter of the permalloy circular dot exceeds some critical size. The magnetization curvature increases gradually as the diameter increases. Finally, when the diameter is larger than another critical size, the new nonuniform state becomes unstable and a vortex enters the particle. Hence the new nonuniform state plays an intermediate role in the evolution from the quasiuniform state to the vortex state as the diameter increases.

  14. 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

  15. 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.

  16. Spintronic transport through an interacting Rashba dot

    International Nuclear Information System (INIS)

    We investigate the spin-dependent transport property through a quantum wire with local Rashba interaction based on fRG method. The Rashba field forms quasi-bound states which couple to the continuum states with an opposite spin direction. It is found that the transport through the Rashba dot strongly depends on an assumed spin polarization of the continuum states and on the Coulomb interaction U in the dot. The interaction U (U>UC) leads to the appearance of three conductance peaks. Two outer peaks are associated with the Coulomb blockade and the center peak is induced by correlation of the electrons with different spin

  17. Quantum phase transition in trigonal triple quantum dots: The case of quantum dots deviated from particle–hole symmetric point

    International Nuclear Information System (INIS)

    We consider a triple quantum dot system in a triangular geometry with one of the dots connected to metallic leads. We investigate quantum phase transition between local moment phase and Kondo screened strong coupling phase in triple quantum dots where energy levels of dots are deviated from the particle–hole symmetric point. The effect of on-site energy of dots on quantum phase transition between local moment phase and Kondo screened strong coupling phase in triple quantum dots is studied based on the analytical arguments and the numerical renormalization group method. The results show that the critical value of tunnel coupling between side dots decreases when the energy level of embedded dot rises up from the symmetric point to the Fermi level and the critical value increases when the energy levels of two side dots rise up. The study of the influence of on-site-energy changes on the quantum phase transitions in triple quantum dots has the importance for clarifying the mechanism of Kondo screening in triple quantum dots where energy levels of dots are deviated from the particle–hole symmetric point

  18. 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.

  19. 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.

  20. 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.

  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. 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.

  3. 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...... to resolve luminescence lines from individual quantum dots, revealing an atomic-like spectrum of sharp transition lines. A parameter of fundamental importance is the intrinsic linewidth of these transitions. Using high-resolution spectroscopy we have determined the linewidth and investigated its dependence...... on temperature, which gives information about how the exciton confined to the quantum dot interacts with the surrounding lattice....

  4. 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...... developed in the study of single quantum dots, characterized by sharp atomic-like transition lines revealing their zero-dimensional density of states. Substantial information about the fundamental properties of individual quantum dots, as well as their interactions with other dots and the host lattice, can...

  5. Lateral excitonic switching in vertically stacked quantum dots

    Science.gov (United States)

    Jarzynka, Jarosław R.; McDonald, Peter G.; Shumway, John; Galbraith, Ian

    2016-06-01

    We show that the application of a vertical electric field to the Coulomb interacting system in stacked quantum dots leads to a 90° in-plane switching of charge probability distribution in contrast to a single dot, where no such switching exists. Results are obtained using path integral quantum Monte Carlo with realistic dot geometry, alloy composition, and piezo-electric potential profiles. The origin of the switching lies in the strain interactions between the stacked dots hence the need for more than one layer of dots. The lateral polarization and electric field dependence of the radiative lifetimes of the excitonic switch are also discussed.

  6. 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.

  7. 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

  8. 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

  9. 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.

  10. 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

  11. Quantum dot quantum cascade infrared photodetector

    International Nuclear Information System (INIS)

    We demonstrate an InAs quantum dot quantum cascade infrared photodetector operating at room temperature with a peak detection wavelength of 4.3 μm. The detector shows sensitive photoresponse for normal-incidence light, which is attributed to an intraband transition of the quantum dots and the following transfer of excited electrons on a cascade of quantum levels. The InAs quantum dots for the infrared absorption were formed by making use of self-assembled quantum dots in the Stranski–Krastanov growth mode and two-step strain-compensation design based on InAs/GaAs/InGaAs/InAlAs heterostructure, while the following extraction quantum stairs formed by LO-phonon energy are based on a strain-compensated InGaAs/InAlAs chirped superlattice. Johnson noise limited detectivities of 3.64 × 1011 and 4.83 × 106 Jones at zero bias were obtained at 80 K and room temperature, respectively. Due to the low dark current and distinct photoresponse up to room temperature, this device can form high temperature imaging

  12. 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

  13. 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

  14. 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...... chiral 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.......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...

  15. Multiple exciton generation effect in quantum dots

    International Nuclear Information System (INIS)

    Full text: Recently among various investigations in the field of nanophysics a great intensification in studying of multiple exciton generation (MEG) effect in quantum dots at absorption of photons with the energy several times higher than the gap in electronic spectra (hν>>Eg) has been made [1-2]. There have been proposed four theoretical approaches to explain the MEG effect. However, the statistic approach basing on the Fermi theory of multiple pi-mesons generation (1950) is the most adequate related to others. In this work: 1. the results of statistic approach have been generalized; 2. the microscopic mechanism basing on theory of electronic 'shaking' has been proposed; 3. the problem of deviation of mean multiplicity of MEG effect from the Poisson law of fluctuations has been investigated that is a evidence of strong non-linear and non-equilibrium character of exciton generation process; 4. the role of interface electronic states of quantum dot and ligand has been considered by means of perturbation theory of closed states related to surface Tamm electronic states of quantum dot and legend; 5. the problem of size optimization of quantum dot to receive the maximum multiplicity has been studied; 6. the efficiency of MEG effect for the third generation of solar cells has been calculated on the basis of proposed theory. (authors)

  16. Linear Kondo conductance in a quantum dot

    International Nuclear Information System (INIS)

    In a tunnelling experiment across a quantum dot it is possible to change the coupling between the dot and the contacts at will, by properly tuning the transparency of the barriers and the temperature. Gate voltages allow for changes of the relative position of the dot addition energies and the Fermi level of the leads. Here we discuss the two limiting cases: weak and strong coupling in the tunnelling Hamiltonian. In the latter case Kondo resonant conductance can emerge at low temperature in a Coulomb blockade valley. We give a pedagogical approach to the single-channel Kondo physics at equilibrium and review the Nozieres scattering picture of the correlated fixed point. We emphasize the effect of an applied magnetic field and show how an orbital Kondo effect can take place in vertical quantum dots tuned both to an even and to an odd number of electrons at a level crossing. We extend the approach to the two-channel overscreened Kondo case and discuss recent proposals for detecting the non-Fermi liquid fixed point which could be reached at strong coupling

  17. Incipient Wigner localization in circular quantum dots

    Science.gov (United States)

    Ghosal, Amit; Güçlü, A. D.; Umrigar, C. J.; Ullmo, Denis; Baranger, Harold U.

    2007-08-01

    We study the development of electron-electron correlations in circular quantum dots as the density is decreased. We consider a wide range of both electron number, N⩽20 , and electron gas parameter, rs≲18 , using the diffusion quantum Monte Carlo technique. Features associated with correlation appear to develop very differently in quantum dots than in bulk. The main reason is that translational symmetry is necessarily broken in a dot, leading to density modulation and inhomogeneity. Electron-electron interactions act to enhance this modulation ultimately leading to localization. This process appears to be completely smooth and occurs over a wide range of density. Thus there is a broad regime of “incipient” Wigner crystallization in these quantum dots. Our specific conclusions are (i) the density develops sharp rings while the pair density shows both radial and angular inhomogeneity; (ii) the spin of the ground state is consistent with Hund’s (first) rule throughout our entire range of rs for all 4⩽N⩽20 ; (iii) the addition energy curve first becomes smoother as interactions strengthen—the mesoscopic fluctuations are damped by correlation—and then starts to show features characteristic of the classical addition energy; (iv) localization effects are stronger for a smaller number of electrons; (v) finally, the gap to certain spin excitations becomes small at the strong interaction (large rs ) side of our regime.

  18. 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...

  19. Quantum-dot excitons in nanostructured environments

    DEFF Research Database (Denmark)

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

    2010-01-01

    The interaction between light and quantum-dot (QD) excitons is strongly influenced by the environment in which the QD is placed. We have investigated the interaction by measuring the time-resolved spontaneous-emission rate of QD excitons in different nanostructured environments. Thereby, we have...

  20. 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...

  1. 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.

  2. 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.

  3. Photoluminescence of hybrid quantum dot systems

    Czech Academy of Sciences Publication Activity Database

    Král, Karel; Menšík, Miroslav

    2015-01-01

    Roč. 7, č. 4 (2015), 347-349. ISSN 2164-6627 R&D Projects: GA MŠk LH12236; GA MŠk LH12186 Institutional support: RVO:68378271 ; RVO:61389013 Keywords : quantum dots * energy transfer * electron-phonon interaction Subject RIV: BM - Solid Matter Physics ; Magnetism

  4. Grating image with desired shaped dots

    Science.gov (United States)

    Honma, Hideaki; Toda, Toshiki; Takahashi, Susumu; Sawamura, Chikara; Iwata, Fujio

    2000-03-01

    A new type of Grating Image we dominate as `Sparklegram' is presented. The Sparklegram is characterized because it provides high quality and better design flexibility. These features are achieved by constructing it with shaped dots as desired. Each dot can be designed as an individual shape, for example, a star or a triangle. As dot shapes, we can use not only geometric patterns, but also some kind of symbols. Not only flexibility of each consists dot shape, but also the quality of reconstructed image is remarkably increased too. Because of these features, the constructed image with the new type of Grating Image, Sparklegram has high quality and high flexibility. It can be applied to security use, for example on credit-cards, tickets, etc., and also can be applied to the package of software products, CDs, videos and other kind of items requiring security. And with these features of flexibility and high quality, Sparklegram has also advantages to be applied to other use, for example amusement use, comics and game characters' goods and packages.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Language, visual working memory, and dot subtraction: What counts?

    Science.gov (United States)

    Briere, Jennifer L; Campbell, Jamie I D

    2016-03-01

    To investigate cognitive factors affecting subtraction of visual objects, we adapted the dot subtraction task developed by Pica, Lemer, Izard, and Dehaene (2004), who used it to investigate calculation by the Mundurukú, an indigene group in Brazil that has a limited number word vocabulary. In the dot subtraction task, briefly displayed arrays of moving dots are used to represent the quantities for subtraction. We tested 40 Canadian university students' dot enumeration, Arabic digit subtraction, visual working memory, and performance on the dot subtraction task with dot display durations of 2, 1.5, 1, and .5 s. In the 2 s condition, error rates were uniformly low, whereas in the .5 s condition, error rates increased sharply as the minuend increased from 4 to 8, as was observed with the Mundurukú. Individual differences in dot subtraction accuracy were predicted by dot enumeration skill with longer dot display durations but were predicted by visual working memory efficiency with shorter durations. Pica et al. (2004) attributed the Mundurukú participants' very poor subtraction to the absence of counting words, but our results show that a shift to reliance on visual working memory is a nonlinguistic factor that comes into play in the dot subtraction task when time to encode the dot arrays is limited. (PsycINFO Database Record PMID:26372056

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

    International Nuclear Information System (INIS)

    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

  11. Coherence and dephasing in self-assembled quantum dots

    DEFF Research Database (Denmark)

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

    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 cohere...... 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.......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...

  12. 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.

  13. Optical Properties of Quantum-Dot-Doped Liquid Scintillators

    CERN Document Server

    Aberle, C; Weiss, S; Winslow, L

    2013-01-01

    Semiconductor nanoparticles (quantum dots) were studied in the context of liquid scintillator development for upcoming neutrino experiments. The unique optical and chemical properties of quantum dots are particularly promising for the use in neutrinoless double beta decay experiments. Liquid scintillators for large scale neutrino detectors have to meet specific requirements which are reviewed, highlighting the peculiarities of quantum-dot-doping. In this paper, we report results on laboratory-scale measurements of the attenuation length and the fluorescence properties of three commercial quantum dot samples. The results include absorbance and emission stability measurements, improvement in transparency due to filtering of the quantum dot samples, precipitation tests to isolate the quantum dots from solution and energy transfer studies with quantum dots and the fluorophore PPO.

  14. Optically controlled spins in semiconductor quantum dots

    Science.gov (United States)

    Economou, Sophia

    2010-03-01

    Spins in charged semiconductor quantum dots are currently generating much interest, both from a fundamental physics standpoint, as well as for their potential technological relevance. Being naturally a two-level quantum system, each of these spins can encode a bit of quantum information. Optically controlled spins in quantum dots possess several desirable properties: their spin coherence times are long, they allow for all-optical manipulation---which translates into fast logic gates---and their coupling to photons offers a straightforward route to exchange of quantum information between spatially separated sites. Designing the laser fields to achieve the unprecedented amount of control required for quantum information tasks is a challenging goal, towards which there has been recent progress. Special properties of hyperbolic secant optical pulses enabled the design of single qubit rotations, initially developed about the growth axis z [1], and later about an arbitrary direction [2]. Recently we demonstrated our theoretical proposal [1] in an ensemble of InAs/GaAs quantum dots by implementing ultrafast rotations about the z axis by an arbitrary angle [3], with the angle of rotation as a function of the optical detuning in excellent agreement with the theoretical prediction. We also developed two-qubit conditional control in a quantum dot `molecule' using the electron-hole exchange interaction [4]. In addition to its importance in quantum dot-based quantum computation, our two-qubit gate can also play an important role in photonic cluster state generation for measurement-based quantum computing [5]. [1] S. E. Economou, L. J. Sham, Y. Wu, D. S. Steel, Phys. Rev. 74, 205415 (2006) [2] S. E. Economou and T. L. Reinecke, Phys. Rev. Lett., 99, 217401 (2007) [3] A. Greilich, S. E. Economou et al, Nature Phys. 5, 262 (2009) [4] S. E. Economou and T. L. Reinecke, Phys. Rev. B, 78, 115306 (2008) [5] S. E. Economou, N. H. Lindner, and T. Rudolph, in preparation

  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. 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.

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. 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...... and the continuum. Additional to the conventional time-domain modeling scheme, a small-signal perturbation analysis has been used to assist the investigation of harmonic modulation properties. The static properties of quantum dot devices, for example high saturation power, have been quantitatively analyzed....... Additional to the static linear amplication properties, we focus on exploring the gain dynamics on the time scale ranging from sub-picosecond to nanosecond. In terms of optical signals that have been investigated, one is the simple sinusoidally modulated optical carrier with a typical modulation frequency...

  3. Quantum features of semiconductor quantum dots

    International Nuclear Information System (INIS)

    The exact solutions of the two-dimensional Schrodinger equation with the position-dependent mass for the square well potential in the semiconductor quantum dots system are obtained. The eigenvalues, which are closely related to the position-dependent masses μ1 and μ2, the potential well depth V0 and the radius of the quantum dots r0, can be calculated from two boundary conditions. We generalize this quantum system to three-dimensional case. The special cases for the angular momentum quantum number l=0, 1, 2 are studied in some detail. We find that the energy levels are proportional to the parameters μ2, V0 and r0 for l=0. The relations between them for l=1, 2 become very complicated. The scattering states of this quantum system are mentioned briefly

  4. Quantum dot/glycol chitosan fluorescent nanoconjugates

    Science.gov (United States)

    Mansur, Alexandra AP; Mansur, Herman S.

    2015-04-01

    In this study, novel carbohydrate-based nanoconjugates combining chemically modified chitosan with semiconductor quantum dots (QDs) were designed and synthesised via single-step aqueous route at room temperature. Glycol chitosan (G-CHI) was used as the capping ligand aiming to improve the water solubility of the nanoconjugates to produce stable and biocompatible colloidal systems. UV-visible (UV-vis) spectroscopy, photoluminescence (PL) spectroscopy, and Fourier transform infrared (FTIR) spectroscopy were used to characterise the synthesis and the relative stability of biopolymer-capped semiconductor nanocrystals. The results clearly demonstrated that the glycol chitosan derivative was remarkably effective at nucleating and stabilising semiconductor CdS quantum dots in aqueous suspensions under acidic, neutral, and alkaline media with an average size of approximately 2.5 nm and a fluorescent activity in the visible range of the spectra.

  5. Thermal annealing of selected individual quantum dots

    International Nuclear Information System (INIS)

    Cathodoluminescence spectra of single InAs/GaAs quantum dots were recorded before and after consecutive thermal annealing steps. The annealing process leads to an overall blueshift of the spectra indicating In/Ga interdiffusion. Excitonic fine-structure splitting and binding energies of charged and neutral excitonic complexes were monitored. A drastic reduction of the fine-structure splitting from 170 μeV to less than 20 μeV can be observed accompanied by a change of the character of the biexciton from anti-binding to binding with respect to the exciton. Tailoring the fine-structure splitting is especially important for the use of single quantum dots in opto-electronic devices for quantum key distribution where a degeneracy of the exciton ground state (i.e. a fine-structure splitting below the homogeneous linewidth) is required for the on-demand production of entangled photon pairs

  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. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Trajectory phases of a quantum dot model

    International Nuclear Information System (INIS)

    We present a thermodynamic formalism to study the trajectories of charge transport through a quantum dot coupled to two leads in the resonant-level model. We show that a close analogue of equilibrium phase transitions exists for the statistics of transferred charge; by tuning an appropriate ‘counting field’, crossovers to different trajectory phases are possible. Our description reveals a mapping between the statistics of a given device and current measurements over a range of devices with different dot–lead coupling strengths. Furthermore insight into features of the trajectory phases are found by studying the occupation of the dot conditioned on the transported charge between the leads; this is calculated from first principles using a trajectory biased two-point projective measurement scheme. (paper)

  12. 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 ...

  13. Lyophilization of Semiconducting Polymer Dot Bioconjugates

    OpenAIRE

    Sun, Wei; Ye, Fangmao; Gallina, Maria E.; Yu, Jiangbo; Wu, Changfeng; Chiu, Daniel T.

    2013-01-01

    Semiconducting polymer dot (Pdot) bioconjugates are a new class of ultrabright fluorescent probes. Here, we report a procedure for lyophilizing Pdot bioconjugates so that they successfully retain their optical properties, colloidal stability, and cell-targeting capability during storage. We found that when Pdot bioconjugates were lyophilized in the presence of 10% sucrose, the rehydrated Pdot bioconjugates did not show any signs of aggregation and exhibited the same hydrodynamic diameters as ...

  14. 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...

  15. 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.

  16. Quantum dot/glycol chitosan fluorescent nanoconjugates

    OpenAIRE

    Mansur, Alexandra AP; Mansur, Herman S.

    2015-01-01

    In this study, novel carbohydrate-based nanoconjugates combining chemically modified chitosan with semiconductor quantum dots (QDs) were designed and synthesised via single-step aqueous route at room temperature. Glycol chitosan (G-CHI) was used as the capping ligand aiming to improve the water solubility of the nanoconjugates to produce stable and biocompatible colloidal systems. UV-visible (UV–vis) spectroscopy, photoluminescence (PL) spectroscopy, and Fourier transform infrared (FTIR) spec...

  17. Kondo Effect in Mesoscopic Quantum Dots

    OpenAIRE

    Grobis, M.; Rau, I. G.; Potok, R. M.; Goldhaber-Gordon, D.

    2006-01-01

    A dilute concentration of magnetic impurities can dramatically affect the transport properties of an otherwise pure metal. This phenomenon, known as the Kondo effect, originates from the interactions of individual magnetic impurities with the conduction electrons. Nearly a decade ago, the Kondo effect was observed in a new system, in which the magnetic moment stems from a single unpaired spin in a lithographically defined quantum dot, or artificial atom. The discovery of the Kondo effect in a...

  18. 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...

  19. 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...

  20. 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...

  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. Thermodynamic properties of a quantum Hall anti-dot interferometer

    Science.gov (United States)

    Levy Schreier, Sarah; Stern, Ady; Rosenow, Bernd; Halperin, Bertrand I.

    2016-02-01

    We study quantum Hall interferometers in which the interference loop encircles a quantum anti-dot. We base our study on thermodynamic considerations, which we believe reflect the essential aspects of interference transport phenomena. We find that similar to the more conventional Fabry-Perot quantum Hall interferometers, in which the interference loop forms a quantum dot, the anti-dot interferometer is affected by the electro-static Coulomb interaction between the edge modes defining the loop. We show that in the Aharonov-Bohm regime, in which effects of fractional statistics should be visible, is easier to access in interferometers based on anti-dots than in those based on dots. We discuss the relevance of our results to recent measurements on anti-dots interferometers.

  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. Controlling quantum dot energies using submonolayer bandstructure engineering

    International Nuclear Information System (INIS)

    We demonstrate control of energy states in epitaxially-grown quantum dot structures formed by stacked submonolayer InAs depositions via engineering of the internal bandstructure of the dots. Transmission electron microscopy of the stacked sub-monolayer regions shows compositional inhomogeneity, indicative of the presence of quantum dots. The quantum dot ground state is manipulated not only by the number of deposited InAs layers, but also by control of the thickness and material composition of the spacing layers between submonolayer InAs depositions. In this manner, we demonstrate the ability to shift the quantum dot ground state energy at 77 K from 1.38 eV to 1.88 eV. The results presented offer a potential avenue towards enhanced control of dot energies for a variety of optoelectronic applications.

  7. Quantum Dot Device Design Optimization for Resonator Coupling

    Science.gov (United States)

    King, Cameron; Coppersmith, S. N.; Friesen, Mark

    Coupling a semiconductor quantum dot qubit to a superconducting resonator broadens the possibilities for interqubit communication and potentially allows integration of quantum dots with other qubit systems. The major technological hurdle that must be overcome is reaching the strong coupling limit, where the coupling frequency between the resonator and the qubit is larger than both the qubit decoherence rate and the photon loss rate of the resonator. In this work, we examine optimization of the quantum dot device design. Using the Thomas-Fermi approximation in conjunction with a metallic dot capacitive model, we focus on improving the capacitive coupling between a resonator gate and a quantum dot while decreasing the cross-coupling to nearby dots. Through these simulations, we find that the optimization follows an intuitive geometric relation. This work was supported in part by ARO (W911NF-12-0607), NSF (PHY-1104660), and ONR (N00014-15-1-0029).

  8. 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.

  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 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.

  11. The quantum Hall effect in quantum dot systems

    International Nuclear Information System (INIS)

    It is proposed to use quantum dots in order to increase the temperatures suitable for observation of the integer quantum Hall effect. A simple estimation using Fock-Darwin spectrum of a quantum dot shows that good part of carriers localized in quantum dots generate the intervals of plateaus robust against elevated temperatures. Numerical calculations employing local trigonometric basis and highly efficient kernel polynomial method adopted for computing the Hall conductivity reveal that quantum dots may enhance peak temperature for the effect by an order of magnitude, possibly above 77 K. Requirements to potentials, quality and arrangement of the quantum dots essential for practical realization of such enhancement are indicated. Comparison of our theoretical results with the quantum Hall measurements in InAs quantum dot systems from two experimental groups is also given

  12. Central dot sign in entities other than Caroli disease

    International Nuclear Information System (INIS)

    The purpose of this study was to describe central dot sign (tiny dots with strong contrast enhancement of the portal vein within dilated hepatic bile ducts on computed tomography) in entities other than Caroli disease, especially in peribiliary cysts with or without autosomal-dominant polycystic kidney disease. Computed tomography in 74 cases of peribiliary cysts and 134 cases of other liver diseases and states possibly showing central dot sign were retrospectively reviewed to examine the central dot sign. In three cases of peribiliary cysts, some part of the liver showed strongly enhanced portal radicles surrounded completely or partially by low-attenuation, enlarged peribiliary cysts, presenting ''central dot sign'' on contrast-enhanced computed tomography. We suggest that in addition to Caroli disease, some other entities and diseases of the liver may demonstrate central dot sign and this sign should not be considered a specific finding of Caroli disease. (author)

  13. Central dot sign in entities other than Caroli disease

    Energy Technology Data Exchange (ETDEWEB)

    Ahmadi, T.; Itai, Yuji [Tsukuba Univ., Ibaraki (Japan). Inst. of Clinical Medicine; Minami, Manabu

    1997-11-01

    The purpose of this study was to describe central dot sign (tiny dots with strong contrast enhancement of the portal vein within dilated hepatic bile ducts on computed tomography) in entities other than Caroli disease, especially in peribiliary cysts with or without autosomal-dominant polycystic kidney disease. Computed tomography in 74 cases of peribiliary cysts and 134 cases of other liver diseases and states possibly showing central dot sign were retrospectively reviewed to examine the central dot sign. In three cases of peribiliary cysts, some part of the liver showed strongly enhanced portal radicles surrounded completely or partially by low-attenuation, enlarged peribiliary cysts, presenting ``central dot sign`` on contrast-enhanced computed tomography. We suggest that in addition to Caroli disease, some other entities and diseases of the liver may demonstrate central dot sign and this sign should not be considered a specific finding of Caroli disease. (author)

  14. 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.

  15. 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.

  16. InAs/InP quantum dots: from single to coupled dots applications

    Energy Technology Data Exchange (ETDEWEB)

    Cornet, C.; Dore, F.; Even, J.; Loualiche, S. [LENS-UMR FOTON 6082 au CNRS, INSA de Rennes, 20 Avenue des Buttes de Coesmes, 35043 Rennes Cedex (France); Schliwa, A.; Bimberg, D. [Institut fuer Festkoerperphysik, Technische Universitaet Berlin, Hardenbergstrasse 36, 10623 Berlin (Germany); Hayne, M.; Moshchalkov, V.V. [INPAC, Pulsed Fields Group, Katholieke Universiteit Leuven, Celestijnenlaan 200D, 3001 Leuven (Belgium); Chauvin, N.; Bremond, G.; Bru-Chevallier, C. [LPM-UMR CNRS 5511, INSA de Lyon, 69621 Villeurbanne Cedex (France); Gendry, M. [LEOM-UMR CNRS 5512, Ecole centrale de Lyon, 69134 Ecully Cedex (France)

    2006-07-01

    We report a brief overview of recent research developments on InAs/InP quantum dots (QDs). Eight-band k . p calculations are performed on single InAs/InP QDs, and the impact of substrate orientation ((311)B or (100)) on electronic and optical properties is studied. A configuration interaction model is used to determine few-particle states of these dots and a comparison with micro-photoluminescence experiments on single InAs/InP QDs is made. It is then demonstrated that high QDs density can be reached on such a system, leading to lateral coupling between dots. Calculations and (magnetophoto-) (photo-) (electro-) luminescence experiments are used to demonstrate that the lateral coupling leads to miniband effects, and to a better charge carrier redistribution between QDs for laser applications. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. InAs/InP quantum dots: from single to coupled dots applications

    International Nuclear Information System (INIS)

    We report a brief overview of recent research developments on InAs/InP quantum dots (QDs). Eight-band k . p calculations are performed on single InAs/InP QDs, and the impact of substrate orientation ((311)B or (100)) on electronic and optical properties is studied. A configuration interaction model is used to determine few-particle states of these dots and a comparison with micro-photoluminescence experiments on single InAs/InP QDs is made. It is then demonstrated that high QDs density can be reached on such a system, leading to lateral coupling between dots. Calculations and (magnetophoto-) (photo-) (electro-) luminescence experiments are used to demonstrate that the lateral coupling leads to miniband effects, and to a better charge carrier redistribution between QDs for laser applications. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. 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)

  19. 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...

  20. 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...... 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....

  1. Unraveling the mesoscopic character of quantum dots in nanophotonics

    OpenAIRE

    Tighineanu, Petru; Sørensen, Anders Søndberg; Stobbe, Søren; Lodahl, Peter

    2014-01-01

    We provide a microscopic theory for semiconductor quantum dots that explains the pronounced deviations from the prevalent point-dipole description that were recently observed in spectroscopic experiments on quantum dots in photonic nanostructures. At the microscopic level the deviations originate from structural inhomogeneities generating a large circular quantum current density that flows inside the quantum dot over mesoscopic length scales. The model is supported by the experimental data, w...

  2. Induced quantum dots and wires: electron storage and delivery

    OpenAIRE

    Bednarek, S.; Szafran, B; R. Dudek; Lis, K.

    2007-01-01

    We show that quantum dots and quantum wires are formed underneath metal electrodes deposited on a planar semiconductor heterostructure containing a quantum well. The confinement is due to the self-focusing mechanism of an electron wave packet interacting with the charge induced on the metal surface. Induced quantum wires guide the transfer of electrons along metal paths and induced quantum dots store the electrons in specific locations of the nanostructure. Induced dots and wires can be usefu...

  3. Thermodynamic properties of a quantum Hall anti-dot interferometer

    OpenAIRE

    Schreier, Sarah Levy; Stern, Ady; Rosenow, Bernd; Halperin, Bertrand I.

    2015-01-01

    We study quantum Hall interferometers in which the interference loop encircles a quantum anti-dot. We base our study on thermodynamic considerations, which we believe reflect the essential aspects of interference transport phenomena. We find that similar to the more conventional Fabry-Perot quantum Hall interferometers, in which the interference loop forms a quantum dot, the anti-dot interferometer is affected by the electro-static Coulomb interaction between the edge modes defining the loop....

  4. 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. PMID:26797087

  5. Metástasis pulmonar miliar como primera manifestación de carcinoma de tiroides bien diferenciado en niños

    Directory of Open Access Journals (Sweden)

    Karol Federico

    2005-02-01

    Full Text Available Objetivo: Presentar el caso de una adolescente con manifestaciones de afectación pulmonar como motivo de consulta, debido a una metástasis pulmonar miliar de carcinoma (Ca papilar de tiroides. Caso Clínico: Se trata de una adolescente femenina de 13 años de edad quien presenta tos seca, disnea de esfuerzo, palpitaciones, dolor precordial, y pérdida de peso de 15 días de evolución. Al examen clínico se evidencia aumento de volumen de la región anterior del cuello a predominio izquierdo, con adenopatía cervical palpable, acrocianosis y cianosis peribucal. Hematología completa, función tiroidea y electrocardiograma normales. La gasometría arterial demuestra una hipoxemia severa. En Rx. de tórax se observa infiltrado miliar micro y macronodular bilateral. En ultrasonido impresionan adenopatías de ubicación pretraqueal y paracarotideas. Tomografía de cuello revela imagen altamente sugestiva de malignidad en lóbulo tiroideo izquierdo y tomografía toraco-abdominal muestra infiltrado pulmonar bilateral micronodular sugestivo de lesiones metastásicas. Estudio histopatológico de ganglio latero cervical izquierdo reporta metástasis de Ca papilar tiroideo a predominio de estructuras foliculares. Se hace diagnóstico de carcinoma papilar bien diferenciado de tiroides con metástasis a región pulmonar, se realiza tiroidectomía total y control de T4L y TSH a los 30 y 60 días post cirugía, con valores normales de T4L y ligeramente aumentados de TSH (7 uU/ml, planteándose metástasis pulmonares funcionantes. Se indica terapia ablativa con I131 presentando evolución clínica estable, pero con cifras de 300 mg/dL de tiroglobulina a los seis meses, por lo que se planifica otra sesión con radioyodo. A propósito de este caso, el segundo en cinco años en la Unidad de Endocrinología del IAHULA, se lleva a cabo una revisión de la literatura sobre esta entidad nosológica. Conclusiones: En niños, el Ca papilar de tiroides puede ponerse

  6. Oscillatory instabilities in dc-biased quantum dots

    International Nuclear Information System (INIS)

    We consider a 'quantum dot' in the Coulomb blockade regime, subject to an arbitrarily large source-drain voltage V. When V is small, quantum dots with odd electron occupation display the Kondo effect, giving rise to enhanced conductance. Here we investigate the regime where V is increased beyond the Kondo temperature and the Kondo resonance splits into two components. It is shown that interference between them results in spontaneous oscillations of the current through the dot. The theory predicts the appearance of 'Shapiro steps' in the current-voltage characteristics of an irradiated quantum dot; these would constitute an experimental signature of the predicted effect. (author). Letter-to-the-editor

  7. 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

  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. 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...

  10. 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...... further 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....

  11. 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.

  12. Core–shell quantum dots: Properties and applications

    International Nuclear Information System (INIS)

    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

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

    OpenAIRE

    Chusseau, Laurent; Philippe, Fabrice; Viktorovitch, Pierre; 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 ...

  14. 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.

  15. 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.

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

    International Nuclear Information System (INIS)

    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

  17. 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.

  18. 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。

  19. 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...

  20. 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...

  1. 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 ...

  2. Éduquer au bien-être animal en formation professionnelle : prise en compte de l'empathie interspécifique par le système éducatif

    OpenAIRE

    Vidal, Michel

    2014-01-01

    Les débats scientifico-éthiques relevant du bien-être animal en font une question socialement vive. Nous interrogeons son enseignement en formation agricole, envisagé au travers d'une éducation à l'empathie interspécifique. Nous questionnons les facteurs des éducations formelle, non-formelle et informelle susceptibles de le défavoriser. Notre recherche se fonde sur les discours de 7 élèves en formation relevant de l'élevage d'animaux de production ou d'animaux de compagnie, de 5 enseignants e...

  3. Riesgos en el proceso de importación ordinaria: identificación del mapa de riesgos de la importación de bienes de capital en Colombia

    OpenAIRE

    Gallón Perdomo, Sara María; Torres Muskus, Carlos Henrique

    2014-01-01

    En Colombia, durante el proceso de importación se presentan diversos riesgos, que pueden implicar desde sobrecostos hasta la pérdida de la mercancía -- Considerando que las importaciones son necesarias en las empresas, en la presente investigación se elabora un mapa de riesgos del proceso de importación ordinaria de bienes de capital en el país, con el fin de identificarlos, de tal manera que los importadores estén informados y puedan aplicar los métodos de control pertinentes para la adm...

  4. 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...

  5. 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...

  6. 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...

  7. 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...

  8. Intersubband Electronic Properties of InAs/GaAs Quantum Dot Molecules with Horizontal Spacer

    OpenAIRE

    A. Khaledi-Nasab; Shahzadeh, M.; Amouzegar, H.; Sabaeian, M.

    2013-01-01

    In this work the intersubband electronic properties of two laterally coupled dome-shaped InAs/GaAs quantum dots were investigated. The envelope functions and eigenenergies were calculated as function of distance between the dots. The coupling between the dots was studied using transition lifetime between the dots. The results showed that in close distances (smaller than 3 nm) the quantum dots are coupled and by increasing the distance transition lifetime fall down drastically and the dots bec...

  9. Homogeneous linewidth of self-assembled III-V quantum dots observed in single-dot photoluminescence

    DEFF Research Database (Denmark)

    Leosson, K.; Birkedal, Dan; Magnúsdóttir, Ingibjörg; Langbein, W.; Hvam, Jørn Märcher

    2003-01-01

    We report photoluminescence emission from single self-assembled InAlGaAs quantum dots, which is broadened purely by dephasing processes. We observe linewidths as low as 6+/-3@meV at 10K, which agrees with the homogeneous linewidth derived from four-wave mixing experiments. By selecting dots that...... are not affected by local field fluctuations and using high-energy excitation, we avoid additional sources of linewidth broadening typically present in single-dot photoluminescence spectra. We observe a strong LO-phonon coupling in InAlGaAs and InGaAs dots, which becomes the dominating contribution to...

  10. The Effectiveness of Family-Based DOTS versus Professional-Family Mix DOTS in Treating Smears Positive Tuberculosis

    Directory of Open Access Journals (Sweden)

    Hassan Yekrang Sis

    2014-07-01

    Full Text Available Background: The present study compared the effectiveness of Family-Based DOTS (FB-DOTS versus Professional-Family Mix DOTS (PFM-DOTS in smear positive tuberculosis (TB patients. Methods: This semi-experimental study was performed in Tuberculosis and Lung Diseases Research Center of Tabriz in 2011-2012, among 57 TB patients recruited into either FB-DOTS or PFM-DOTS groups. At the baseline of the study, knowledge of both patients and their supervisors were assessed while at the end point, smear and culture of sputum, quality of life, knowledge and satisfaction of the patients along with the knowledge and satisfaction of their super-visors were assessed. Results: The difference for sputum smear negative (culture was 16.2 (4.8% and 7.7(6.9% for the PFM-DOTS in comparison with FB DOTS by the end of the second and forth months of treatment, respectively. A significant difference was observed between the two groups in relation to knowledge, satisfaction (patients and supervisors and all four domains of quality of life: physical health (P=0.036, psychological health (P<0.001, social relations (P=0.026 and environmental health (P<0.001. Conclusion: The PFM-DOTS treatment strategy in which health experts follow the patients in their homes seems to be among most appropriate strategies in treating TB.

  11. 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

  12. Evaluación y análisis de la mejora del servicio de autorización de exportación del Registro de Bienes Culturales de Matanzas

    Directory of Open Access Journals (Sweden)

    Justa Bielka Cantillo González

    2011-04-01

    Full Text Available La presente investigación se realiza en el Registro Provincial de Bienes Culturales de Matanzas, donde se implementa un procedimiento creado por el colectivo de la Cátedra de Calidad de la Universidad de Matanzas “Camilo Cienfuegos” para la evaluación y análisis de la mejora del servicio de autorización exportación de bienes culturales.Para desarrollar la investigación se aplicaron las siguientes herramientas: Diagrama de Flujo, Diagrama Causa-Efecto, Encuesta, Análisis Operacional,  Estadística descriptiva, no paramétrica, y multivariada (paquete estadístico SPSS, versión 15.0, Modelos de Frontera (Software EMS, Software Visio, Instrumento Servqual modificado.Los resultados obtenidos en el estudio permitieron comprobar que de los indicadores gestionados por la organización el indicador más afectado es la eficacia y que existen reservas de eficiencia en las que se debe continuar trabajando. Se realiza el análisis causal de los indicadores afectados y se proponen medidas para la mejora de los mismos.

  13. 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.

  14. A Nanowire-Based Plasmonic Quantum Dot Laser.

    Science.gov (United States)

    Ho, Jinfa; Tatebayashi, Jun; Sergent, Sylvain; Fong, Chee Fai; Ota, Yasutomo; Iwamoto, Satoshi; Arakawa, Yasuhiko

    2016-04-13

    Quantum dots enable strong carrier confinement and exhibit a delta-function like density of states, offering significant improvements to laser performance and high-temperature stability when used as a gain medium. However, quantum dot lasers have been limited to photonic cavities that are diffraction-limited and further miniaturization to meet the demands of nanophotonic-electronic integration applications is challenging based on existing designs. Here we introduce the first quantum dot-based plasmonic laser to reduce the cross-sectional area of nanowire quantum dot lasers below the cutoff limit of photonic modes while maintaining the length in the order of the lasing wavelength. Metal organic chemical vapor deposition grown GaAs-AlGaAs core-shell nanowires containing InGaAs quantum dot stacks are placed directly on a silver film, and lasing was observed from single nanowires originating from the InGaAs quantum dot emission into the low-loss higher order plasmonic mode. Lasing threshold pump fluences as low as ∼120 μJ/cm(2) was observed at 7 K, and lasing was observed up to 125 K. Temperature stability from the quantum dot gain, leading to a high characteristic temperature was demonstrated. These results indicate that high-performance, miniaturized quantum dot lasers can be realized with plasmonics. PMID:27030886

  15. 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

  16. 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

  17. Fractional decay of quantum dots in photonic crystals

    DEFF Research Database (Denmark)

    Kristensen, Philip Trøst; Koenderink, Femius; Lodahl, Peter; Tromborg, Bjarne; Mørk, Jesper

    2008-01-01

    We define a practical measure for the degree of fractional decay and establish conditions for the effect to be observable for quantum dots in photonic crystals exhibiting absorptive losses.......We define a practical measure for the degree of fractional decay and establish conditions for the effect to be observable for quantum dots in photonic crystals exhibiting absorptive losses....

  18. 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

  19. 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...

  20. Coherent Dynamics of Quantum Dots in Photonic-Crystal Cavities

    DEFF Research Database (Denmark)

    Madsen, Kristian Høeg

    deviations. Similar measurements on a quantum dot in a photonic-crystal cavity sow a Rabi splitting on resonance, while time-resolved measurements prove that the system is in the weak coupling regime. Whle tuning the quantum dot through resonance of the high-Q mode we observe a strong and surprisingly...

  1. 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...

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

    DEFF Research Database (Denmark)

    Ballou, Byron; Ernst, Lauren A.; Andreko, Susan; Fitzpatrick, James A. J.; Lagerholm, B. Christoffer; Bruchez, Marcel; Waggoner, Alan S.

    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...

  3. 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

  4. X-ray scattering from periodic arrays of quantum dots

    International Nuclear Information System (INIS)

    Three-dimensional periodic arrays of self-organized quantum dots in semiconductor multilayers are investigated by high-resolution x-ray scattering. We demonstrate that the statistical parameters of the dot array can be determined directly from the scattering data without performing a numerical simulation of the scattered intensity.

  5. Quantum dots for multimodal molecular imaging of angiogenesis

    OpenAIRE

    Mulder, W.J.M.; Strijkers, G.J.; Nicolay, K.; Griffioen, A W

    2010-01-01

    Quantum dots exhibit unique optical properties for bioimaging purposes. We have previously developed quantum dots with a paramagnetic and functionalized coating and have shown their potential for molecular imaging purposes. In the current mini-review we summarize the synthesis procedure, the in vitro testing and, importantly, the in vivo application for multimodal molecular imaging of tumor angiogenesis.

  6. Quantum Wires and Quantum Dots for Neutral Atoms

    OpenAIRE

    Schmiedmayer, Joerg

    1998-01-01

    By placing changeable nanofabricated structures (wires, dots, etc.) on an atom mirror one can design guiding and trapping potentials for atoms. These potentials are similar to the electrostatic potentials which trap and guide electrons in semiconductor quantum devices like quantum wires and quantum dots. This technique will allow the fabrication of nanoscale atom optical devices.

  7. 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

  8. 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.

  9. 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

  10. Resonant Raman scattering off neutral quantum dots

    International Nuclear Information System (INIS)

    Resonant inelastic (Raman) light scattering off neutral GaAs quantum dots which contain a mean number, N=42, of electron-hole pairs is computed. We find Raman amplitudes corresponding to strongly collective final states (charge-density excitations) of similar magnitude as the amplitudes related to weakly collective or single-particle excitations. As a function of the incident laser frequency or the magnetic field, they are rapidly varying amplitudes. It is argued that strong Raman peaks should come out in the spin-density channels, not related to valence-band mixing effects in the intermediate states. (author)

  11. 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

  12. Quantum-dot excitons in nanostructured environments

    DEFF Research Database (Denmark)

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

    2010-01-01

    The interaction between light and quantum-dot (QD) excitons is strongly influenced by the environment in which the QD is placed. We have investigated the interaction by measuring the time-resolved spontaneous-emission rate of QD excitons in different nanostructured environments. Thereby, we have...... determined the oscillator strength, quantum efficiency and spin-flip rates of QD excitons as well as their dependencies on emission wavelength and QD size. Enhancement and inhibition of QD spontaneous emission in photonic crystal membranes (PCMs) is observed. Efficient coupling to PCM waveguides is...

  13. Quantum-dot excitons in nanostructured environments

    DEFF Research Database (Denmark)

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

    2011-01-01

    The interaction between light and quantum-dot (QD) excitons is strongly influenced by the environment in which the QD is placed. We have investigated the interaction by measuring the time-resolved spontaneous-emission rate of QD excitons in different nanostructured environments. Thereby, we have...... determined the oscillator strength, quantum efficiency and spin-flip rates of QD excitons as well as their dependencies on emission wavelength and QD size. Enhancement and inhibition of QD spontaneous emission in photonic crystal membranes (PCMs) is observed. Efficient coupling to PCM waveguides is...

  14. Relaxation dynamics in correlated quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Andergassen, S. [Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna (Austria); Schuricht, D.; Pletyukhov, M.; Schoeller, H. [Institute for Theory of Statistical Physics, RWTH Aachen University and JARA-Fundamentals of Future Information Technology, 52056 Aachen (Germany)

    2014-12-04

    We study quantum many-body effects on the real-time evolution of the current through quantum dots. By using a non-equilibrium renormalization group approach, we provide analytic results for the relaxation dynamics into the stationary state and identify the microscopic cutoff scales that determine the transport rates. We find rich non-equilibrium physics induced by the interplay of the different energy scales. While the short-time limit is governed by universal dynamics, the long-time behavior features characteristic oscillations as well as an interplay of exponential and power-law decay.

  15. 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

  16. 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.

  17. 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.

  18. Silicon quantum dots: fine-tuning to maturity.

    Science.gov (United States)

    Morello, Andrea

    2015-12-18

    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. PMID:26584678

  19. Charge-tunable indium gallium nitride quantum dots

    Science.gov (United States)

    Zhang, Lei; Teng, Chu-Hsiang; Ku, Pei-Cheng; Deng, Hui

    2016-02-01

    III-Nitride quantum dots have emerged as a new chip-scale system for quantum information science, which combines electrical and optical interfaces on a semiconductor chip that is compatible with noncryogenic operating temperatures. Yet most work has been limited to optical excitations. To enable single-spin-based quantum optical and quantum information research, we demonstrate here quantized charging in optically active, site-controlled III-nitride quantum dots. Single-electron charging was confirmed by the voltage dependence of the energy, dipole moment, fine structures, and polarization properties of the exciton states in the quantum dots. The fundamental energy structures of the quantum dots were identified, including neutral and charged excitons, fine structures of excitons, and A and B excitons. The results lay the ground for coherent control of single charges in III-nitride quantum dots, opening a door to III-nitride-based spintronics and spin-qubit quantum information processing.

  20. 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.

  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. Representative longitudinal optical phonon modes in polar semiconductor quantum dots

    International Nuclear Information System (INIS)

    Highlights: ► We model the exciton-longitudinal optical phonon coupling for cylinder quantum dot. ► We predict a representative optical phonon mode for GaAs/AlAs quantum dot. ► Huang–Rhys factors increases with radius decreasing of GaAs/AlAs quantum dot. - Abstract: Existence of representative longitudinal optical (LO) phonon modes is theoretically discussed for the case of polar semiconductor cylindrical quantum dots embedded in a semiconductor matrix. The approach is developed within the dielectric continuum model considering the Fröhlich interaction between electrons and the confined LO phonons. The theory is applied to cylindrical GaAs/AlAs quantum dots within an adiabatic treatment.

  3. Electric and Magnetic Interaction between Quantum Dots and Light

    DEFF Research Database (Denmark)

    Tighineanu, Petru

    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......-quadrupole contributions and may compete with the dipole moment in light-matter interactions. A theory for the quantum-dot wavefunctions is developed showing that the mesoscopic moment originates from distortions in the underlying crystal lattice. The resulting quantum-mechanical current density is curved leading to light......-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...

  4. Quantum dot systems: artificial atoms with tunable properties

    International Nuclear Information System (INIS)

    Full text: Quantum dots - also called zero-dimensional electron systems or artificial atoms - are physical objects where the constituent electrons are confined in a small spatial region, leading to discrete eigenvalues for the energies of the confined electrons. Large quantum dots offer a dense energy spectrum comparable to that of metallic grains, whereas small quantum dots more closely resemble atoms in their electronic properties. Quantum dots can be linked to leads by tunnel barriers, hence permitting electrical transport measurements: Coulomb blockade and single-electron charging effects are observed due to the repulsive electron electron interaction on the quantum dot site. Usually fabricated by conventional semiconductor growth and processing technology, the advantage is that both simple and also more complex quantum dot systems can be designed to purpose, acting as model systems with in-situ tunable parameters such as the number of confined electrons in the quantum dot and the strength of the tunnel coupling to the leads, electrostatically controlled by the applied voltages to gate electrodes. With increasing the tunnel coupling to the leads, the virtual occupation of the quantum dot from the leads becomes more and more important -- the simple description of electrical transport by single-electron tunneling events breaks down. The basic physics is described by the Kondo physics based on the Anderson impurity model. A system consisting of strongly electrostatically coupled quantum dots with separate leads to each quantum dot represent another realization of the Anderson impurity model. Experiments to verify the analogy are presented. The experimental data embedded within this tutorial have been obtained with Alexander Huebel, Matthias Keller, Joerg Schmid, David Quirion, Armin Welker, Ulf Wilhelm, and Klaus von Klitzing. (author)

  5. 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.

  6. 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...

  7. 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

  8. 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.

  9. Quantum chaos in open quantum dot arrays

    International Nuclear Information System (INIS)

    Full text: The discovery of chaos in macro-scale physical systems led to the emergence of a new understanding of laws in nature. Chaos should not exist at all in quantum systems - as laws of quantum mechanics actually forbid it. We will show in this work the footprints of quantum chaos in the dynamics of electron transport by studying ballistic open quantum dot arrays. We will apply quantum mechanical calculations and classical calculations in order to explain the low field magneto-transport through open quantum dots. To characterize the quantum/classical correspondence in this system and to understand the transport, it is necessary to invoke dynamical tunneling, a quantum-mechanical mechanism which allows tunneling of electrons between chaotic and regular regions in the phase space, a process which is classically forbidden. The relevant conclusions regarding dynamical tunneling are drawn by using Husimi representations. By comparing the classical trajectories with the electron probability density high accordance is achieved. The Husimi plots are used to visualize the wave function distribution in the vx-x-plane of the Poincare section. We show in the Husimi plots that the wave function has weight on the regular and chaotic regions alike. This represents a distribution in the phase space that cannot be generated by classical dynamics and supports the interpretation including dynamical tunneling. (author)

  10. 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)

  11. 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.

  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. 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.

  14. Coherent coupling of two quantum dots embedded in an Aharonov-Bohm ring

    OpenAIRE

    Holleitner, A. W.; Decker, C. R.; Eberl, K.; Blick, R. H.

    2000-01-01

    We define two laterally gated small quantum dots (~ 15 electrons) in an Aharonov-Bohm geometry in which the coupling between the two dots can be broadly changed. For weakly coupled quantum dots we find Aharonov-Bohm oscillations. In an intermediate coupling regime we concentrate on the molecular states of the double dot and extract the magnetic field dependence of the coherent coupling.

  15. A Ge/Si heterostructure nanowire-based double quantum dot with integrated charge sensor

    DEFF Research Database (Denmark)

    Hu, Yongjie; Churchill, Hugh; Reilly, David;

    2007-01-01

    between the dots and to the leads. We also demonstrate a novel approach to charge sensing in a one-dimensional nanostructure by capacitively coupling the double dot to a single dot on an adjacent nanowire. The double quantum dot and integrated charge sensor serve as an essential building block required to...

  16. 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....

  17. Zeros in single-channel transmission through double quantum dots.

    Science.gov (United States)

    Rotter, I; Sadreev, A F

    2005-04-01

    By using a simple model we consider single-channel transmission through a double quantum dot that consists of two single dots coupled by a wire of finite length L . Each of the two single dots is characterized by a few energy levels only, and the wire is assumed to have only one level whose energy depends on the length L . The transmission is described by using S matrix theory and the effective non-Hermitian Hamilton operator H(eff) of the system. The decay widths of the eigenstates of H(eff) depend strongly on energy. The model explains the origin of the transmission zeros of the double dot that is considered by us. Mostly, they are caused by (destructive) interferences between neighboring levels and are of first order. When, however, both single dots are identical and their transmission zeros are of first order, those of the double dot are of second order. First-order transmission zeros cause phase jumps of the transmission amplitude by pi, while there are no phase jumps related to second-order transmission zeros. In this latter case, a phase jump occurs due to the fact that the width of one of the states vanishes when crossing the energy of the transmission zero. The parameter dependence of the widths of the resonance states is determined by the spectral properties of the two single dots. PMID:15903767

  18. 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.

  19. 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.

  20. 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...

  1. 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.

  2. 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, ...

  3. La virtud y el comercio en el pensamiento de Domingo de Soto: las prácticas comerciales, el carácter y el bien común

    OpenAIRE

    Azevedo-Alves, A. (André); Moreira, J M

    2014-01-01

    El artículo ahonda en la obra de Domingo de Soto, teólogo, filósofo y especialista en ética del siglo XVI, y examina su propuesta, basada en la virtud, de una evaluación ética del comercio dentro de un marco aristotélico-tomista que permite la articulación de los negocios y el bien común. Presta particular atención al énfasis fundamental que Soto pone en la distinción entre el comercio como actividad y la conducta específica de las personas que se dedican a la actividad comercial. La distinci...

  4. 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 ...

  5. Attitudes et consentement à payer des consommateurs vis-à-vis du bien-être animal : une application au cas de la viande bovine en France et en Espagne

    OpenAIRE

    Weisslinger, Delphine

    2015-01-01

    L’intérêt pour le bien-être animal (BEA) se manifeste de plus en plus dans nos sociétés européennes, et peut conduire à de nouvelles attentes de la part les consommateurs. Cette étude s’intéresse aux attitudes et au Consentement à Payer (CAP) des consommateurs pour de la viande bovine certifiée « respectueuse du BEA », à l’aide d’une enquête menée auprès de 1213 consommateurs répartis dans quatre régions en France et en Espagne. La mesure des degrés d’importance et de confiance accordés à 11 ...

  6. 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...

  7. 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.

  8. Coupling capacitance between double quantum dots tunable by the number of electrons in Si quantum dots

    International Nuclear Information System (INIS)

    Tunability of capacitive coupling in the Si double-quantum-dot system is discussed by changing the number of electrons in quantum dots (QDs), in which the QDs are fabricated using pattern-dependent oxidation (PADOX) of a Si nanowire and multi-fine-gate structure. A single QD formed by PADOX is divided into multiple QDs by additional oxidation through the gap between the fine gates. When the number of electrons occupying the QDs is large, the coupling capacitance increases gradually and almost monotonically with the number of electrons. This phenomenon is attributed to the gradual growth in the effective QD size due to the increase in the number of electrons in the QDs. On the other hand, when the number of electrons changes in the few-electron regime, the coupling capacitance irregularly changes. This irregularity can be observed even up to 40 electrons. This behavior is attributable the rough structure of Si nano-dots made by PADOX. This roughness is thought to induce complicated change in the electron wave function when an electron is added to or subtracted from a QD

  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...... processes with relevant acoustic phonons. We show that the relaxation is dominated by phonon-assisted electron tunneling between constituent quantum dots and occurs on a picosecond time scale. The dependence of the time evolution of the quantum dot occupation probabilities on the energy mismatch between the...

  10. 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

  11. 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.

  12. 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.

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

    DEFF Research Database (Denmark)

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

    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...

  14. 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.

  15. 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.

  16. 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.

  17. Imaging GABAc Receptors with Ligand-Conjugated Quantum Dots

    Directory of Open Access Journals (Sweden)

    Sandra J. Rosenthal

    2008-04-01

    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.

  18. 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.

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

    International Nuclear Information System (INIS)

    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

  20. 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

  1. Generation of even harmonics in coupled quantum dots

    International Nuclear Information System (INIS)

    Using the spatial-temporal symmetry principle we developed recently, we propose an effective scheme for even-harmonics generation in coupled quantum dots. The relative intensity of odd and even harmonic components in the emission spectrum can be controlled by tuning the dipole couplings among the dots, which can be realized in experiments by careful design of the nanostructures. In particular, pure 2nth harmonics and (2n+1)th harmonics (where n is an integer) can be generated simultaneously with polarizations in two mutual perpendicular directions in our systems. An experimental design of the coupled dots system is presented.

  2. 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 ...

  3. Voltage recovery in charged InAs/GaAs quantum dot solar cells

    OpenAIRE

    Lam, P.; Hatch, S.; Wu, J.; Tang, M.; Dorogan, V. G.; Mazur, Y. I.; Salamo, G. J.; Ramiro, I.; Seeds, A.; Liu, H

    2014-01-01

    The realization of high efficiency quantum dot intermediate band solar cells is challenging due to the thermally activated charge escaping at high temperatures. The enhancement in short circuit current of quantum dot solar cells is largely undermined by the voltage loss. In this paper, InAs/GaAs quantum dot solar cells with direct Si doping in the quantum dots are studied. The open circuit voltage is improved with increasing doping concentration in the quantum dots. The recovery of open circu...

  4. 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.

  5. On the Dynamics of Single-Electron Tunneling in Semiconductor Quantum Dots under Microwave Radiation

    OpenAIRE

    Qin, Hua

    2001-01-01

    Efforts are made in this thesis to reveal the dynamics of single-electron tunneling and to realize quantum bits (qubits) in semiconductor quantum dots. At low temperatures, confined single quantum dots and double quantum dots are realized in the twodimensional electron gas (2DEG) of AlGaAs/GaAs heterostructures. For transport studies, quantum dots are coupled to the drain and source contacts via tunnel barriers. Electron-electron interaction in such closed quantum dots leads to...

  6. Internal transitions of magnetoexcitons in quantum dots

    International Nuclear Information System (INIS)

    Systems of Ne and Nh holes in a strong magnetic field and confined in a quasi two-dimensional region are studied. The first quantum well sub-band approximation was used. For the theoretical description of this highly interacting system, the Hamiltonian is diagonalized in a basis of Stater determinants. The energy levels and wave functions are found to different values of the total angular momentum M and the magnetic field B. Oscillator strengths for transitions involving the ground state are calculated. The dependence on B and Ne, for Nh = 1, of the position and magnitude of the most prominent transitions is found. This study is of interest for the analysis of linear and non linear optical properties related to intra-band transitions in quantum dots formed in semiconductor heterostructures. (author)

  7. 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.

  8. 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

  9. 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.

  10. 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

  11. Spectroscopic behavior of bioconjugated quantum dots

    Science.gov (United States)

    Chornokur, G.; Ostapenko, S.; Emirov, Yu; Korsunska, N. E.; Sellers, T.; Phelan, C.

    2008-07-01

    We report on a short-wavelength, 'blue' spectral shift of the photoluminescence (PL) spectrum in CdSeTe/ZnS core/shell quantum dots (QDs) caused by bioconjugation with several monoclonal cancer-related antibodies (ABs). Scanning PL spectroscopy was performed on samples dried on solid substrates at various temperatures. The influence of the AB chemical origin on the PL spectral shift was observed. The QD-AB conjugation reaction was confirmed using the agarose gel electrophoresis technique. The spectral shift was strongly increased and the process facilitated when the samples were dried above room temperature. The PL spectroscopic mapping revealed a profile of the PL spectral shift across the dried QD-AB spot. A mechanism of the blue shift is attributed to changes in the QD electronic energy levels caused by a local stress applied to the bioconjugated QD.

  12. 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.

  13. 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

  14. 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.

  15. 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

  16. 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.

  17. 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).

  18. Luminescence upconversion in colloidal double quantum dots.

    Science.gov (United States)

    Deutsch, Zvicka; Neeman, Lior; Oron, Dan

    2013-09-01

    Luminescence upconversion nanocrystals capable of converting two low-energy photons into a single photon at a higher energy are sought-after for a variety of applications, including bioimaging and photovoltaic light harvesting. Currently available systems, based on rare-earth-doped dielectrics, are limited in both tunability and absorption cross-section. Here we present colloidal double quantum dots as an alternative nanocrystalline upconversion system, combining the stability of an inorganic crystalline structure with the spectral tunability afforded by quantum confinement. By tailoring its composition and morphology, we form a semiconducting nanostructure in which excited electrons are delocalized over the entire structure, but a double potential well is formed for holes. Upconversion occurs by excitation of an electron in the lower energy transition, followed by intraband absorption of the hole, allowing it to cross the barrier to a higher energy state. An overall conversion efficiency of 0.1% per double excitation event is achieved. PMID:23912060

  19. Fire test of DOT 7A Boxes

    International Nuclear Information System (INIS)

    The primary objective of conducting the full-scale fire tests of the DOT (Department of Transportation) 7A FRP Boxes was to provide information to assist in quantifying the fire hazard of the storage located at the Radioactive Waste Management Complex (RWMC), and to learn if changing the storage array will decrease the fire risk. Also, the level of fire fighting and fire protection required to maintain the risk at the RWMC within acceptable DOE guidelines was investigated. Two full-scale fire tests were conducted at Southwest Research Institute (SwRI) in June 1978, using the DOE 7A FRP Plywood Storage Containers. The fire tests showed that when subjected to a substantial ignition source, the boxes will propagate fire as long as no fire-suppression measures are taken. Fire will breach the boxes and spread the radioactive contaminated waste if it is not extinguished. As the fire progresses, additional boxes will become involved, and eventually the entire storage array will ignite. It is recommended that the use of DOT 7A Boxes be discontinued and replaced with noncombustible storage containers. In the event this is not practicable, guidance recommendations are presented to minimize the large fire loss potential. It is also recommended that an investigation be conducted into the number of boxes that can be destroyed and still maintain a safe environment for employees and the public. This investigation should include how far radioactive contamination will spread, what cleanup will be required, anticipated exposure of the people within the area, and the public impact of such a fire

  20. 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

  1. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Pozner, R.; Lifshitz, E. [Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa 32000 (Israel); Solid State Institute, Technion-Israel Institute of Technology, Haifa 32000 (Israel); Russell Berrie Nanotechnology Institute, Technion-Israel Institute of Technology, Haifa 32000 (Israel); Peskin, U., E-mail: uri@tx.technion.ac.il [Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa 32000 (Israel); Russell Berrie Nanotechnology Institute, Technion-Israel Institute of Technology, Haifa 32000 (Israel); Lise Meitner Center for Computational Quantum Chemistry, Technion-Israel Institute of Technology, Haifa 32000 (Israel)

    2015-09-14

    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.

  3. Gate-controlled electromechanical backaction induced by a quantum dot

    Science.gov (United States)

    Okazaki, Yuma; Mahboob, Imran; Onomitsu, Koji; Sasaki, Satoshi; Yamaguchi, Hiroshi

    2016-04-01

    Semiconductor-based quantum structures integrated into mechanical resonators have emerged as a unique platform for generating entanglement between macroscopic phononic and mesocopic electronic degrees of freedom. A key challenge to realizing this is the ability to create and control the coupling between two vastly dissimilar systems. Here, such coupling is demonstrated in a hybrid device composed of a gate-defined quantum dot integrated into a piezoelectricity-based mechanical resonator enabling milli-Kelvin phonon states to be detected via charge fluctuations in the quantum dot. Conversely, the single electron transport in the quantum dot can induce a backaction onto the mechanics where appropriate bias of the quantum dot can enable damping and even current-driven amplification of the mechanical motion. Such electron transport induced control of the mechanical resonator dynamics paves the way towards a new class of hybrid semiconductor devices including a current injected phonon laser and an on-demand single phonon emitter.

  4. 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...

  5. 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

  6. 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.

  7. Correlation studies in weakly confining quantum dot potentials

    Science.gov (United States)

    Kimani, Peter; Jones, Preston; Winkler, Peter

    We investigate the electron correlation in few-electron closed-shell atomic systems and similarly in few-electron quantum dots under weak confinement. As usual we start with restricted Hartree-Fock (HF) calculations and add electron correlation in steps in a series of approximations based on the single particle Green's function approach: (i) second-order Green function (GF); (ii) 2ph-Tamm-Dancoff approximation (TDA); and (iii) an extended version thereof which introduces ground-state correlation into the TDA. Our studies exhibit similarities and differences between weakly confined quantum dots and standard atomic systems. The calculations support the application of HF, GF, and TDA techniques in the modeling of three-dimensional quantum dot systems. The observed differences emphasize the significance of confinement and electronic features unique to quantum dots, such as the increased binding of electrons with higher angular momentum and thus - compared to atomic systems - modified shell-filling sequences.

  8. Nonequilibrium electron transport through quantum dots in the Kondo regime

    DEFF Research Database (Denmark)

    Wölfle, Peter; Paaske, Jens; Rosch, Achim; Kroha, Johann

    2005-01-01

    Electron transport at large bias voltage through quantum dots in the Kondo regime is described within the perturbative renormalization group extended to nonequilibrium. The conductance, local magnetization, dynamical spin susceptibility and local spectral function are calculated. We show how the ...

  9. Nodal ground states and orbital textures in semiconductor quantum dots

    Czech Academy of Sciences Publication Activity Database

    Lee, J.; Výborný, Karel; Han, J.E.; Žutič, I.

    2014-01-01

    Roč. 89, č. 4 (2014), "045315-1"-"045315-17". ISSN 1098-0121 Institutional support: RVO:68378271 Keywords : quantum dots * electronic structure Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.736, year: 2014

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. What future for quantum dot-based light emitters?

    Science.gov (United States)

    Nurmikko, Arto

    2015-12-01

    Synthesis of semiconductor colloidal quantum dots by low-cost, solution-based methods has produced an abundance of basic science. Can these materials be transformed to high-performance light emitters to disrupt established photonics technologies, particularly semiconductor lasers?

  15. Classical treatment of electrons in open quantum dots

    International Nuclear Information System (INIS)

    Full text: Electronic transport through open quantum dots has received much attention in recent years. The dot system is defined using finger gate structures on top of a 2DES in an AIGaAs/GaAs heterostructure. We perform magneto-resistance measurements in open quantum dots for different gate voltages that show several resistance maxima at certain magnetic fields. In a model calculation with constrictions of varying width and a parabolic anisotropic confinement potential (soft-wall) we demonstrate that this peaks may be associated with commensurate backscattered orbits. We compare our soft-wall calculations with those using a hard-wall potential. While both models yield the same position of the two-reflection trajectory, the positions for the trajectories with more than two reflections differ. The experimental results agree significantly better with the soft-wall results, thus supporting this kind of confinement for open dots defined by split gate structures. (author)

  16. Photon Cascade from a Single Crystal Phase Nanowire Quantum Dot

    DEFF Research Database (Denmark)

    Bouwes Bavinck, Maaike; Jöns, Klaus D; Zieliński, Michal; Patriarche, Gilles; Harmand, Jean-Christophe; Akopian, Nika; Zwiller, Val

    2016-01-01

    unprecedented potential to be controlled with atomic layer accuracy without random alloying. We show for the first time that crystal phase quantum dots are a source of pure single-photons and cascaded photon-pairs from type II transitions with excellent optical properties in terms of intensity and line width......We report the first comprehensive experimental and theoretical study of the optical properties of single crystal phase quantum dots in InP nanowires. Crystal phase quantum dots are defined by a transition in the crystallographic lattice between zinc blende and wurtzite segments and therefore offer....... We notice that the emission spectra consist often of two peaks close in energy, which we explain with a comprehensive theory showing that the symmetry of the system plays a crucial role for the hole levels forming hybridized orbitals. Our results state that crystal phase quantum dots have promising...

  17. 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.

  18. 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.

  19. The multilayered spherical quantum dot under a magnetic field

    International Nuclear Information System (INIS)

    The binding energy of an impurity located at the center of multilayered spherical quantum dot (MSQD) is reported as a function of the dot and barrier thickness for different alloy compositions under the influence of a magnetic field. Within the effective mass approximation, the binding energy has been calculated using the fourth order Runge-Kutta method without magnetic field. A variational approach has been employed if a magnetic field is present. The binding energy in MSQD with equal dot and barrier thickness is calculated. It is shown that the binding energy in MSQD differs from that of a single quantum dot. Also, the geometry is dominant on the binding energy for thin MSQDs, but the magnetic field becomes more effective for thick MSQDs.

  20. 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.

  1. 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....

  2. 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...

  3. Microwave spectroscopy on a quantum-dot molecule

    OpenAIRE

    Oosterkamp, T. H.; Fujisawa, T.; van der Wiel, W. G.; Ishibashi, K.; Hijman, R. V.; Tarucha, S.; Kouwenhoven, L. P.

    1998-01-01

    Quantum dots are small conductive regions in a semiconductor, containing a variable number of electrons (N=1 to 1000) that occupy well defined discrete quantum states. They are often referred to as artificial atoms with the unique property that they can be connected to current and voltage contacts. This allows one to use transport measurements to probe the discrete energy spectra. To continue the analogy with atoms, two quantum dots can be connected to form an 'artificial molecule'. Depending...

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

    DEFF Research Database (Denmark)

    Madsen, Kristian Høeg; Ates, Serkan; Lund-Hansen, Toke; Löffler, Andreas; Reitzenstein, Stephan; Forchel, Alfred; Lodahl, Peter

    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.......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....

  5. 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.

  6. 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.

  7. 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...

  8. 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....

  9. Conceptual design of a DOT farm generator station

    OpenAIRE

    Michailidis, D.; Diepeveen, N.F.B.

    2011-01-01

    The Delft Offshore Turbine (DOT) is a DUWIND research project that focuses on reducing the cost of offshore wind energy by bringing a radical change in offshore wind turbine technology. The main concept is to centralize electricity generation by having individual wind turbines create a flow of pressurized seawater to a hydropower station. The idea behind the DOT is that the high power to weight ratio from hydraulic drive systems gives the opportunity for a reduced nacelle mass and increased r...

  10. Relaxation of quantum-dot electrons in a microcavity

    International Nuclear Information System (INIS)

    We report on theoretical results concerning the relaxation of electrons in parabolic quantum dots embedded in a planar microcavity. Following an external femtosecond pulse, the electron and cavity radiation systems exchange energy in a non-monotonic way. One of the salient features of this system is a staircase-like time evolution as a consequence of the coherent superposition of quantum-dot excited states caused by the ultra-short pump pulse. (Author)

  11. Relaxation of quantum-dot electrons in a microcavity

    Energy Technology Data Exchange (ETDEWEB)

    Paris, R. [Departamento de Fisica, Universidad Javeriana, Apartado aereo 56710, Bogota (Colombia); Quiroga, L.; Rodriguez, F.J. [Departamento de Fisica, Universidad de Los Andes, Apartado aereo 4976, Bogota (Colombia)

    1998-12-31

    We report on theoretical results concerning the relaxation of electrons in parabolic quantum dots embedded in a planar microcavity. Following an external femtosecond pulse, the electron and cavity radiation systems exchange energy in a non-monotonic way. One of the salient features of this system is a staircase-like time evolution as a consequence of the coherent superposition of quantum-dot excited states caused by the ultra-short pump pulse. (Author)

  12. 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....

  13. 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....

  14. 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...

  15. 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...

  16. 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...

  17. 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...

  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. Nondestructive measurement of electron spins in a quantum dot

    OpenAIRE

    Meunier, T.; Vink, I. T.; Willems van Beveren, L.H.; Koppens, F. H. L.; Tranitz, H. P.; Wegscheider, W.; Kouwenhoven, L. P.; Vandersypen, L. M. K.

    2006-01-01

    We propose and implement a nondestructive measurement that distinguishes between two-electron spin states in a quantum dot. In contrast to earlier experiments with quantum dots, the spins are left behind in the state corresponding to the measurement outcome. By measuring the spin states twice within a time shorter than the relaxation time T1, correlations between the outcomes of consecutive measurements are observed. They disappear as the wait time between measurements becomes comparable to T...

  20. Detecting Majorana fermions by nonlocal entanglement between quantum dots

    OpenAIRE

    Wang, Zhi; Hu, Xiao

    2011-01-01

    Nonlocal entanglement between two quantum dots can be generated through Majorana fermions. The two Majorana fermions at the ends of an one-dimensional topological superconductor form a nonlocal fermion level, coupling to the occupation states of two quantum dots put close to the two ends, and the entire system will come into an entangled state. After introducing a charging energy by a capacitor, entanglement of the entire system can manifest itself through the nonlocal entanglement between th...