647 research outputs found

    DNA-Powered Stimuli-Responsive Single-Walled Carbon Nanotube Junctions

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    Reconfigurable stimuli-responsive molecular materials play an important role in the fabrication of nanoscale systems and devices. Here, we report a bottom-up strategy for the reversible assembly of single-walled carbon nanotube linear junctions in solution. The assembly/disassembly of the nanotubes can be controlled via the intrinsic responsiveness to different stimuli of sequence-specific deoxyribonucleic acid linkers forming the junctions

    Decomposition of Ruthenium Olefin Metathesis Catalysts

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    The decomposition of a series of ruthenium metathesis catalysts has been examined using methylidene species as model complexes. All of the phosphine-containing methylidene complexes decomposed to generate methylphosphonium salts, and their decomposition routes followed first-order kinetics. The formation of these salts in high conversion, coupled with the observed kinetic behavior for this reaction, suggests that the major decomposition pathway involves nucleophilic attack of a dissociated phosphine on the methylidene carbon. This mechanism also is consistent with decomposition observed in the presence of ethylene as a model olefin substrate. The decomposition of phosphine-free catalyst (H_2IMes)(Cl)_2Ru CH(2-C_6H_4-O-i-Pr) (H_2IMes = 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene) with ethylene was found to generate unidentified ruthenium hydride species. The novel ruthenium complex (H_2IMes)(pyridine)_3(Cl)_2Ru, which was generated during the synthetic attempts to prepare the highly unstable pyridine-based methylidene complex (H_2IMes)(pyridine)_2(Cl)_2Ru CH_2, is also reported

    Individualizando la Tutoría del Alumno de Ingeniería

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    Es un hecho conocido por los profesores universitarios, por experiencia propia, que el uso de la tutoría presencial que hace el alumnado es de escasa entidad. Una prospección elemental entre el alumnado nos ha llevado a identi ficar varias causas que motivan tan bajo aprovechamiento de este recurso. El objetivo de esta experiencia de innovación ha sido la adaptación de la tutoría a las necesidades concretas de cada alumno, previa identi ficación de las mismas mediante el uso del Campus Virtual. Para ello, cada clase teórica ha fi nalizado con la identifi cación de los conceptos que el alumno no ha captado bien, mediante una serie de preguntas a contestar de forma inmediata presentadas mediante el campus virtual de la asignatura, y respondidas en tiempo real por los estudiantes. Una vez identi ficadas, se invierten los roles; es el profesor quien demanda la presencia del alumno en la tutoría, con el objeto de cubrir las lagunas que previamente ha identi ficado. Los resultados obtenidos muestran que el modelo planteado mejora los resultados fi nales de nuestros alumnos.It is a fact known by university professors, from their own experience, that the use of face-to-face tutoring by students is limited. An elementary prospecting among the students has led us to identify several causes that motivate such a low use of this resource. The objective of this innovation experience has been the adaptation of the tutorial to the specific needs of each student, after identifying them by using the Virtual Campus. For this, each theoretical class has ended with the identification of the concepts that the student has not grasped well, through a series of questions to answer immediately presented through the virtual campus of the subject, and answered in real time by the students. students. Once identi fi ed, the roles are reversed; it is the teacher who demands the presence of the student in the tutoring, in order to cover the gaps that he has previously identified. The results obtained show that the proposed model improves the final results of our students.Universidad de Granada: Departamento de Arquitectura y Tecnología de Computadore

    Dynamic Speckle Laser technique for the characterization of electrotechnical-porcelain

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    This work analyzes the quality of two types of commercial electro-technical-porcelain using textural and physical-chemical methods: BET surface area and pore size by gas adsorption, X-ray powder diffraction; Electronic Microscopy and Energy dispersive X-ray analysis, Infrared Spectroscopy and their water adsorption capacity by the Dynamic Speckle Laser technique. Experimental results showed the evolution of the speckle patterns during hydro-adsorption process, permitting to discriminate different behavior for each material. It was determined that it is possible to correlate changes in the speckle patterns with the porosity and chemical composition of materials

    White-tailed deer (Odocoileus virginianus) positively affect the growth of mature northern red oak (Quercus rubra) trees

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    Understanding and predicting the effects of deer (Cervidae) on forest ecosystems present significant challenges in ecosystem ecology. Deer herbivory can cause large changes in the biomass and species composition of forest understory plant communities, including early life-cycle trees (i.e., seedlings and saplings). Such changes can impact juvenile to adult transitions and the future age structure and species composition of mature forests. Changes to understory vegetation also impact flow of energy and nutrients in forest ecosystems. Studies examining the influence of deer on mature trees, however, are rare and rely on extrapolating effects from early life cycle stages of trees. We tested the hypothesis that the absence of deer would result in an increase in the growth rate of mature trees by examining the impact of white-tailed deer (Odocoileus virginianus) on mature canopy trees. We examined incremental growth in individuals of Quercus rubra, an important component of temperate deciduous forests in North America, inside and outside 16-year deer exclosures in eastern U.S. deciduous forests. We found that adult trees inside exclosures grew less than those directly exposed to deer. Our findings highlight the indirect effects of white-tailed deer on the growth of adult individuals of Q. rubra in a way opposite of what would be expected from previous studies based on immature or understory tree populations. We suggest the increased growth of adult trees in the presence of deer may be explained by increased nutrient inputs through deer fecal and urine deposits and the alteration of the competitive environment belowground through the reduction of understory vegetation by browsing. Underscoring the ecological and demographic importance of adult trees in forest ecosystems, results from this study suggest the direct and indirect effects of deer on mature trees should not be overlooked

    Upper Limb Posture Estimation in Robotic and Virtual Reality-based Rehabilitation.

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    New motor rehabilitation therapies include virtual reality (VR) and robotic technologies. In limb rehabilitation, limb posture is required to (1) provide a limb realistic representation in VR games and (2) assess the patient improvement. When exoskeleton devices are used in the therapy, the measurements of their joint angles cannot be directly used to represent the posture of the patient limb, since the human and exoskeleton kinematic models differ. In response to this shortcoming, we propose a method to estimate the posture of the human limb attached to the exoskeleton. We use the exoskeleton joint angles measurements and the constraints of the exoskeleton on the limb to estimate the human limb joints angles. This paper presents (a) the mathematical formulation and solution to the problem, (b) the implementation of the proposed solution on a commercial exoskeleton system for the upper limb rehabilitation, (c) its integration into a rehabilitation VR game platform, and (d) the quantitative assessment of the method during elbow and wrist analytic training. Results show that this method properly estimates the limb posture to (i) animate avatars that represent the patient in VR games and (ii) obtain kinematic data for the patient assessment during elbow and wrist analytic rehabilitation

    Recomendaciones para la informatización de los servicios de neonatología

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    El objetivo es proporcionar el marco para la recopilación de datos en el área de la salud de los recién nacidos que permitan la armonización de la asistencia sea cual sea su lugar de nacimiento. Para ello es necesario conocer la población atendida y la mayor dificultad es la ausencia de un sistema de recopilación de datos y de unos estándares asistenciales para todas las condiciones del recién nacido. Es imprescindible disponer de un registro único en el que se recojan los principales datos perinatales y neonatales de todos los recién nacidos. La Sociedad Española de Neonatología (SEN) debe ser el depositario y responsable de la base de datos, que debe cumplir todas las exigencias legales de privacidad y confidencialidad. A nivel de cada centro es posible conocer el peso relativo de la afección atendida por grupos de diagnósticos relacionados (DRG) y los resultados desde el aspecto de calidad asistencial. Mediante análisis comparativos (estudios de benchmarking,. . .) es posible establecer las pautas de diagnóstico y tratamiento. Es necesario conocer la población de recién nacidos atendida y definir criterios de diagnóstico y tratamiento para mejorar la calidad asistencial. La SEN desea dirigirse a los responsables asistenciales de los centros hospitalarios para pedirles su apoyo y colaboración en la puesta en marcha de estas recomendaciones

    Curling: Content-ubiquitous resolution and delivery infrastructure for next-generation services

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    CURLING, a Content-Ubiquitous Resolution and Delivery Infrastructure for Next Generation Services, aims to enable a future content-centric Internet that will overcome the current intrinsic constraints by efficiently diffusing media content of massive scale. It entails a holistic approach, supporting content manipulation capabilities that encompass the entire content life cycle, from content publication to content resolution and, finally, to content delivery. CURLING provides to both content providers and customers high flexibility in expressing their location preferences when publishing and requesting content, respectively, thanks to the proposed scoping and filtering functions. Content manipulation operations can be driven by a variety of factors, including business relationships between ISPs, local ISP policies, and specific content provider and customer preferences. Content resolution is also natively coupled with optimized content routing techniques that enable efficient unicast and multicast-based content delivery across the global Internet
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