Mostrando recursos 1 - 20 de 339.553

  1. Caracteres foliares en diez especies neotropicales y argentinas de Canna (Cannaceae, Zingiberales)

    Ciciarelli, María de las Mercedes; Passarelli, Lilian Mónica; Rolleri, Cristina Hilda
    Se llevó a cabo un estudio con microscopía de luz y electrónica de barrido (MEB) de los caracteres de la epidermis y de la ontogenia de los estomas en especies neotropicales de Canna (Cannaceae). Se estudiaron la presencia y tipos de indumento, el contorno foliar, los tipos de cera epicuticular, los modelos epidérmicos, el ordenamiento celular típico de epifilos e hipofilos, el espesor de la pared externa de las células epidérmicas y los caracteres de los estomas adultos paracíticos en ejemplares de C. ascendens, C. glauca, C. indica, C. lineata, C. paniculata, C. tandilensis y C. variegatifolia. Los caracteres se...

  2. Microencapsulación de sustancias activas para su incorporación en calzado

    Sánchez Navarro, M. Magdalena
    En los últimos años, el calzado fabricado en España, y en la Unión Europea en general, camina hacia nuevos conceptos en los que la sostenibilidad y la incorporación de los elementos "activos" van a tener un importante papel como valor añadido y elemento de competitividad. Este hecho obliga a los fabricantes de calzado y componentes a reinventarse y desarrollar nuevos productos que cumplan con las exigencias tanto del mercado como de los consumidores. Con los últimos avances en el campo de los materiales funcionales y/o activos se abre una nueva vía para el desarrollo de productos que presenten propiedades funcionales...

  3. Desarrollo de un sistema de transmisión flexible para un robot bio-inspirado

    Hevia Crespo, Antonio
    En la actualidad están ganado importancia y protagonismo los vehículos aéreos no tripulados, o UAV, los conocidos como drones, no solo en los ámbitos científicos, sino también a nivel de la vida cotidiana y el ocio. En este proyecto en concreto se trata con un tipo particular, los vehículos micro aéreos de aleteo, conocidos como FWMAV, que proviene de coger las iniciales de su nombre en inglés (Flapping-Wing Micro Air Vehicles). Muchos FWMAV tienen su inspiración en organismos naturales, imitando sus características de vuelo. En la actualidad la mayoría de los sistemas de transmisión que utilizan este tipo de vehículos son sistemas...

  4. Determination of methane and carbon dioxide surface emissions in a Spanish landfill

    Sánchez Fernández, Carlos; Narros Sierra, Adolfo; Peso Díaz, Maria Isabel del; Fuente García-Soto, María del Mar de la; Rodríguez Hurtado, Encarnación
    Fugitive emissions from the surface of landfills constitute an important source of carbon dioxide and methane that are emitted to the atmosphere and contribute to the greenhouse effects. Quantifying those emissions can give valuable information, not only, on the amount of those gases which are released into the atmosphere but on their environmental consequences. They can also help to evaluate another aspects related to the landfill management like the seal efficiency or the gas recovery. Quantifying these emissions is not an easy task, due to the heterogeneity of the waste into the landfills, their huge dimensions and the influence of others...

  5. Aceros sinterizados al Mo con gradiente funcional

    Ruiz Román, José Manuel; García Cambronero, Luis Enrique; Cisneros Belmonte, Manuel
    Los materiales con gradiente funcional (FGM), los multimateriales, tratan de satisfacer los numerosos requerimientos demandados a las piezas con una combinación determinada de composiciones y microestructuras. La compatibilidad necesaria entre materiales condiciona el proceso de fabricación y el logro de una interfase, no siempre difusa. La metalurgia de polvos es una de las técnicas empleadas en la fabricación de materiales con gradiente funcional y, en concreto la compactación en matriz una de las posibles técnicas de conformado de estos materiales. En el presente trabajo se propone un proceso de conformado de un acero con gradiente funcional que varía su composición...

  6. Evaluación del uso de aditivos de origen natural sobre la propiedades del ácido poliláctico (PLA) para su uso como empaque de alimentos

    Cortés Manrique, José David
    En este trabajo se evaluó el efecto de dos aditivos de origen natural (caolinita y cascarilla de arroz) sobre propiedades mecánicas, térmicas y de permeabilidad del ácido poliláctico. La caolinita fue transformada por adsorción de los ácidos grasos palmítico y laúrico. Los aditivos se caracterizaron por fluorescencia de rayos X, difracción de rayos X, microscopía electrónica de barrido, análisis de energía dispersiva de rayos X (EDX) y espectroscopia infrarroja. Para la evaluación del efecto de los aditivos sobre el ácido poliláctico se usó un diseño experimental de dos factores: tipo de aditivo y concentración del aditivo. El factor concentración se trabajó a dos niveles: 1% y 5%....

  7. UK guideline on transition of adolescent and young persons with chronic digestive diseases from paediatric to adult care

    Brooks, Alenka J.; Smith, Philip J.; Cohen, Richard; Collins, Paul; Douds, Andrew; Forbes, Valda; Gaya, Daniel R.; Johnston, Brian T.; McKiernan, Patrick J.; Murray, Charles D.; Sebastian, Shaji; Smith, Monica; Whitley, Lisa; Williams, Lesley; Russell, Richard K.; McCartney, Sara A.; Lindsay, James O.
    The risks of poor transition include delayed and inappropriate transfer that can result in disengagement with healthcare. Structured transition care can improve control of chronic digestive diseases and long-term health-related outcomes. These are the first nationally developed guidelines on the transition of adolescent and young persons (AYP) with chronic digestive diseases from paediatric to adult care. They were commissioned by the Clinical Services and Standards Committee of the British Society of Gastroenterology under the auspices of the Adolescent and Young Persons (A&YP) Section. Electronic searches for English-language articles were performed with keywords relating to digestive system diseases and transition to...

  8. Structures and Reactions of Diplatinum Complexes

    Darnton, Tania Victoria

    A d8−d8 complex [Pt2(μ-P2O5(BF2)4]4− (abbreviated Pt(pop-BF2)4−) undergoes two 1e reductions at E1/2 = −1.68 and Ep = −2.46 V (vs Fc+/Fc) producing reduced Pt(pop-B2)5− and superreduced Pt(pop-BF2)6− species, respectively. The EPR spectrum of Pt(pop-BF2)5− and UV−vis spectra of both the reduced and the superreduced complexes, together with TD-DFT calculations, reveal successive filling of the 6pσ orbital accompanied by gradual strengthening of Pt−Pt bonding interactions and, because of 6pσ delocalization, of Pt−P bonds in the course of the two reductions. Both reduction steps proceed without changing either d8 Pt electronic configuration, making the superreduced Pt(pop-BF2)6− a very rare 6p2 σ-bonded binuclear...

  9. First-principles calculations of thermal, electrical, and thermoelectric transport properties of semiconductors

    Zhou, Jiawei; Liao, Bolin; Chen, Gang
    The transport properties of semiconductors are key to the performance of many solid-state devices (transistors, data storage, thermoelectric cooling and power generation devices, etc). An understanding of the transport details can lead to material designs with better performances. In recent years simulation tools based on first-principles calculations have been greatly improved, being able to obtain the fundamental ground-state properties of materials (such as band structure and phonon dispersion) accurately. Accordingly, methods have been developed to calculate the transport properties based on an ab initio approach. In this review we focus on the thermal, electrical, and thermoelectric transport properties of semiconductors,...

  10. Object Removal in Panoramic Media

    MacQuarrie, A; Steed, A
    Due in large part to new consumer virtual reality systems, panoramic media is an increasingly popular image and video format. While the capture of panoramic media is well understood, editing still poses many challenges. In this paper we explore object removal in 360° images. First, a method is proposed in which field-of-view expansion using retargeting techniques is combined with Graphcut Textures to remove objects near the equator of the viewing sphere. Several extensions and refinements are proposed to improve this technique, including how it can be extended to removing objects anywhere on the viewing sphere. Secondly, inpainting in 360° images is examined,...

  11. CHERI: A Hybrid Capability-System Architecture for Scalable Software Compartmentalization

    Watson, RNM; Woodruff, J; Neumann, PG; Moore, SW; Anderson, J; Chisnall, D; Dave, N; Davis, B; Gudka, K; Laurie, B; Murdoch, SJ; Norton, R; Roe, M; Son, S; Vadera, M
    CHERI extends a conventional RISC Instruction-Set Architecture, compiler, and operating system to support fine-grained, capability-based memory protection to mitigate memory-related vulnerabilities in C-language TCBs. We describe how CHERI capabilities can also underpin a hardware-software object-capability model for application compartmentalization that can mitigate broader classes of attack. Prototyped as an extension to the open-source 64-bit BERI RISC FPGA soft-core processor, Free BSD operating system, and LLVM compiler, we demonstrate multiple orders-of-magnitude improvement in scalability, simplified programmability, and resulting tangible security benefits as compared to compartmentalization based on pure Memory-Management Unit (MMU) designs. We evaluate incrementally deployable CHERI-based compartmentalization using several real-world...

  12. Desarrollo de métodos analíticos basados en técnicas cromatográficas y espectrometría de masas para estudios de metalómica de fármacos antitumorales de Pt en muestras biológicas

    Esteban Fernández, Diego
    El Platino (Pt) es un elemento químico de número atómico 78 y que pertenece al grupo 10 de la tabla periódica. Su configuración electrónica es [Xe] 4f14 5d9 6s1. Se trata de un metal de transición blanco grisáceo, precioso, pesado, maleable y dúctil. Es relativamente resistente al ataque químico, presenta buenas propiedades físicas a temperaturas altas y buenas propiedades eléctricas. Por estos motivos se emplea en contactos eléctricos, electrodos, equipamiento de laboratorio, empastes, catalizadores de automóviles y joyería. Fue descubierto en el siglo XVI por el español Antonio de Ulloa en unas minas de oro de Colombia. Es un metal...

  13. Las revistas académicas de comunicación de acceso abierto en México. Retos y vicisitudes

    López Ornelas, Maricela; Osuna Lever, Cecilia; Díaz López, Karla
    Introduction. This research presents the case of communication academic journals in Mexico. It briefly presents some of its background, current state, challenges and difficulties. It also provides the number of undergraduate and graduate communication programs in the country in order to reflect on their current state. Methodology: The work is descriptive and it is based on the review of open access academic publications that treat communication topics and sub-topics. It identifies the characteristics that give them the description of ―academic‖, examines their visibility through database indexing, access formats, use of Open Journal Systems (OJS), inclusion of the digital object identifier (DOI), use of anti-plagiarism programs, adhesion to...

  14. Theoretical and experimental study of the electronic, crystalline, morphologic, compositional, magnetic and dielectric properties of the Sr2D y NbO6 material

    Cardona, Ramiro; Landinez, David; Roa Rojas, Jairo
    We report experimental and theoretical results of crystal structure, morphology, magnetic and electric features, and electronic structure for the Sr2D y NbO6 ceramic compound. Samples were produced by the solid-state reaction recipe. X-ray diffraction experiments show that the material crystallizes in a monoclinic structure, P21/nspace group. SEM images exhibit a granular submicrometric surface. Temperature curves of magnetic susceptibility reveal a paramagnetic response. Curie law fitting permitted to obtain a magnetic moment 10.28μB. Polarization as a function of electric fields shows a hysteretic feature with 264.28 relative dielectric constant at 300 K. DFT calculations of electronic structure suggest the semiconductor character...

  15. Multi-Wavelength Laser Transmitter for the Two-Step Laser Time-of-Flight Mass Spectrometer

    Farcy, Benjamin J.; Grubisic, Andrej; Uckert, Kyle; Li, Steven X.; Li, Xiang; Getty, Stephanie; Yu, Anthony W.; Fahey, Molly E.
    Missions to diverse Outer Solar System bodies will require investigations that can detect a wide range of organics in complex mixtures, determine the structure of selected molecules, and provide powerful insights into their origin and evolution. Previous studies from remote spectroscopy of the Outer Solar System showed a diverse population of macromolecular species that are likely to include aromatic and conjugated hydrocarbons with varying degrees of methylation and nitrile incorporation. In situ exploration of Titan's upper atmosphere via mass and plasma spectrometry has revealed a complex mixture of organics. Similar material is expected on the Ice Giants, their moons, and...

  16. Urban Biomining Meets Printable Electronics: End-To-End at Destination Biological Recycling and Reprinting

    Navarrete, Jesica; Koehne, Jessica; Gandhiraman, Ram; Rothschild, Lynn J.; Spangle, Dylan
    Space missions rely utterly on metallic components, from the spacecraft to electronics. Yet, metals add mass, and electronics have the additional problem of a limited lifespan. Thus, current mission architectures must compensate for replacement. In space, spent electronics are discarded; on earth, there is some recycling but current processes are toxic and environmentally hazardous. Imagine instead an end-to-end recycling of spent electronics at low mass, low cost, room temperature, and in a non-toxic manner. Here, we propose a solution that will not only enhance mission success by decreasing upmass and providing a fresh supply of electronics, but in addition has...

  17. Rational design of a fluopyram hapten and preparation of bioconjugates and antibodies for immunoanalysis

    Ceballos Alcantarilla, Eric; Agulló, Consuelo; Abad Fuentes, Antonio; Abad Somovilla, Antonio; Mercader Badia, Josep Vicent
    A fluopyram hapten was designed in which insignificant electronic and structural modifications were foreseen and all potentially interacting chemical moieties were maintained. This hapten was prepared by total synthesis and three immunologically active bioconjugates were obtained and characterized. High-affinity and specific antibodies to fluopyram were raised.

  18. Educação em química, formação e trabalho docente : revisão de pesquisas brasileiras (2002-2015)

    Fonseca, Carlos Ventura; Santos, Flávia Maria Teixeira dos
    Neste trabalho apresentamos uma revisão da literatura sobre a temática da formação e do trabalho docente e sua relação com a área da Educação em Química, abrangendo 260 artigos que constam na base de dados SciELO - Scientific Electronic Library Online, no período de 2002 a 2015. A metodologia utilizada é definida como análise documental, tendo em vista a riqueza de informações extraídas dos documentos consultados, bem como a estabilidade das fontes de dados. Consideramos os enfoques apresentados pelas pesquisas e as principais críticas que são atribuídas às ações governamentais relacionadas ao tema. Verificamos que, com relação à formação de...

  19. Stereochemical And Synthetic Investigations

    Venu, Lingampally
    PART I RESOLUTION AND DESYMMETRISATION Chapter I. ‘A Novel Racemate Resolution’. This describes a novel resolution strategy as applied to racemic α-amino acids in the solid state. The strategy is based on the possibility that second order asymmetric transformations (SOAT) would be more likely in the case of achiral molecules that form chiral crystals (i.e. a non- centrosymmetric space group).1 In such cases, a fundamental requirement of SOAT – that the molecules racemise in solution prior to crystallization – is obviated. Furthermore, the resulting enantiomerically-enriched crystals may be employed to effect a solid-state kinetic resolution of a different racemate (composed of chiral...

  20. Actividades emprendedoras y espacios alternativos de aprendizaje : desarrollo de competencias durante un "hackathon day" [Recurso electrónico] / Carmen Ruíz Viñals, Eva Perea Muñoz, Vanesa Berlanga Silvente.

    Ruiz Viñals, Carmen.; Berlanga Silvente, Vanesa, coaut.; Perea Muñoz, Eva, coaut.
    En: Doxa Comunicación: revista interdisciplinar de estudios de comunicación y ciencias sociales. ISSN 1696-019X n. XXIV, 2017, pp 175-186

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