A cotunneling mechanism for all-electrical Electron Spin Resonance of single adsorbed atoms

The recent development of all-electrical electron spin resonance (ESR) in a scanning tunneling microscope (STM) setup has opened the door to vast applications. Despite the fast growing number of experimental works on STM-ESR, the fundamental principles remains unclear. By using a cotunneling picture, we show that the spin resonance signal can be explained as a time-dependent variation of the tunnel barrier induced by the alternating electric driving field. We demonstrate how this variation translates into the resonant frequency response of the direct current. Our cotunneling theory explains the main experimental findings. Namely, the linear dependence of the Rabi flop rate with the alternating bias amplitude, the absence of resonant response for spin-unpolarized currents, and the weak dependence on the actual atomic species.Comment: 11 pages, 3 figure

Evolution of the Field of Social Media Research through Science Maps (2008-2017)

The objectives of this work were to discover the main points of interest in the field of research on Social Media, within the scientific area of Communication, and to analyse how it has evolved. A methodology based on the analysis of co-words and visualisation techniques was applied. The data was obtained from scientific publications indexed in the Web of Science (WoS) database, during the periods 2008-2012 and 2013-2017. The resulting maps showed that, during the period 2008-2012, the main areas of interest were web 2.0 and the internet in terms of social networking sites. However, during the period 2013-2017, there was a strong upward trend in the impact of social networks and platforms, especially Twitter and Facebook, in many areas (such as social movements, public relations and publicity, distribution of content, crisis communication, participatory journalism, political communication, or the configuration of public identities through social platforms, with special emphasis on youth). Finally, new scientific challenges were found in automatic analysis of content and management of big data. In conclusion, it was possible to transform a complex, underlying, dynamic and multidimensional reality into visible representations that could help experts in the field to better understand the evolution of research on Social Media.Los objetivos de este trabajo fueron descubrir los principales focos de interés del campo de investigación de los Social Media, dentro del área científica de la Comunicación, y analizar la dinámica de su evolución. Se aplicó una metodología basada en el análisis de co-palabras y en técnicas de visualización. Los datos se obtuvieron de las publicaciones científicas indexadas en la base de datos Web of Science (WoS), durante los períodos temporales 2008-2012 y 2013-2017. Los mapas resultantes mostraron que durante el período 2008-2012 las principales áreas de interés fueron la web 2.0 y el uso de Internet en el ámbito de los medios de comunicación. Sin embargo, durante el período 2013-2017 se apreció una fuerte tendencia ascendente del impacto de las redes y las plataformas sociales, especialmente Twitter y Facebook, en numerosas áreas, tales como los movimientos sociales, las relaciones públicas y la publicidad, la difusión de contenidos, la comunicación de crisis, el periodismo participativo, la comunicación política o la configuración de las identidades públicas a través de las plataforma sociales, con especial incidencia en los adolescentes. Por último, los nuevos retos científicos se situaron en el análisis automático de contenidos y en la gestión de datos masivos, o big data. En conclusión, se consiguió transformar una realidad compleja, subyacente, dinámica y multidimensional en representaciones visibles que podrían ayudar a una mejor comprensión de la evolución del campo de investigación de los Social Media por parte de los expertos en la materia

Effect of Glass Fiber Hybridization on the Behavior Under Impact of Woven Carbon Fiber/Epoxy Laminates

The low-velocity impact behavior was studied in hybrid laminates manufactured by RTM with woven carbon and glass (S2) fabrics. Specimens with different thicknesses and glass fiber content (from 0 to 21 vol.%) were tested with impact energies in the range 30–245 J and the resulting deformation and fracture micromechanisms were studied using X-ray microtomography. The results of these analyses, together with those of the impact tests (maximum load and energy absorbed), were used to elucidate the role played by glass fiber hybridization on the fracture micromechanisms and on the overall laminate performance under low-velocity impact

Nuevas aportaciones al catálogo aeropalinológico de Córdoba: plantas exóticas

Se ha estudiado el pol en de 22 taxones de la flora exótica de la ciudad de Córdoba , posiblemente anemófilos. La presencia de estos taxones es importante en unos casos por su caracter al ergógeno ( Schinus, Ricinus, Aesculus, Elaeagnus y Acacia ); en otros por ser ti picamente en tornó filas (Tipuana, Sophora, Impatiens, Callistemon y Feijoa) y en otros casos por su problemática de recolección o determinación en los mues t reos ( Melia , Libocedrus, Taxodium, Carex, Cyperus, Tilia y Jacaranda).The pollen of 22 taxa posibly anemophilous of the Cór doba exotic flora are stud i ed. In sorne cases the presence of it are i mportant for their alergenic caracter (Schinus, Ricinus 1 Aesculus 1 Elaeagnus and Acacia} ; i n other cases for to be typically ent omoph i lous { Tipuana 1 Sophora, Impatiens, Callistemon and Feijoa ) and in other for t heir prob l ematic collecti ng or identification in the sampl ing ( Melia, Libocedrus 1 Taxodium 1 Carex 1 Cyperus, Tilia and Jacaraoda

Sistemas de evaluación de los alumnos mediante test informatizados utilizando telefonía móvil

This paper describes a system for executing adaptive tests in mobile devices. Tests are generated in XML files using Test Editor that is a author tool integrated in AHA! system. These tests are interpreted by our system that can show to the user in theirs mobile devices such as mobile phone or PDA. Our test execution engine is a Midlet, that is a small Java application oriented to be executed in a mobile device. This application can execute classic or adaptive test of type activity (it can be executed all the times that students wants) or exam (it can be only executed one time). Studens have to identify with theirs logins the first time that they execute a test. The next times is not necessary due to it is stored in the RMS memory. In this memory, we also store the interface adaptable parameters such as the language, the font type, the number of screens in which the question will be shown, etc. Finally, after executing a test the obtained results are shonw to the students and they are also send it to the AHA! server by GPRS.Este artículo presenta un sistema para la ejecución de test adaptativos en dispositivos móviles. Los test son generados en forma de ficheros XML a través de la herramienta autor Test Editor que se encuentra integrada en el sistema AHA! y son interpretados por nuestro sistema que puede mostrarlos a los usuarios en su dispositivo móvil, ya sea teléfono móvil o PDA. Nuestro motor de ejecución de test es un Midlet que es una pequeña aplicación Java orientada a ser ejecutada en dispositivos móviles. Esta aplicación permite realizar test clásicos y adaptativos de tipo actividad y de tipo examen. Si la prueba es de tipo examen, ésta sólo podrá ser ejecutada una sola vez, en cambio si es de tipo actividad se podrá ejecutar tantas veces como se quiera. Los estudiantes deben de identificarse con su login la primera vez que ejecuta el test, ya que el resto de veces éste queda almacenado en memoria RMS. En esta memora tambien son almacenados los parámetros adaptables del interfaz, ya que los estudiantes podrán personalizar la configuración de el idioma, el tipo de fuente, el número de pantallas en que se muestran las preguntas, etc. Finalmente tras ejecutar un test los resultados obtenidos son mostrados a los estudiantes y son tambien enviados al servidor de AHA! a través de GPRS

Human metapneumovirus: Mechanisms and molecular targets used by the virus to avoid the immune system

Indexación: Scopus.This work was supported by Comisión Nacional de Investigación Científica y Tecnolígica (CONICYT) N◦21151028 and FONDECYT (N◦1070352 and N◦1170964) and the Millennium Institute on Immunology and Immunotherapy (P09/016-F).Human metapneumovirus (hMPV) is a respiratory virus, first reported the year 2001. Since then, it has been described as one of the main etiological agents that causes acute lower respiratory tract infections (ALRTIs), which is characterized by symptoms such as bronchiolitis, wheezing and coughing. Susceptible population to hMPV-infection includes newborn, children, elderly and immunocompromised individuals. This viral agent is a negative-sense, single-stranded RNA enveloped virus, that belongs to the Pneumoviridae family and Metapneumovirus genus. Early reports-previous to 2001-state several cases of respiratory illness without clear identification of the responsible pathogen, which could be related to hMPV. Despite the similarities of hMPV with several other viruses, such as the human respiratory syncytial virus or influenza virus, mechanisms used by hMPV to avoid the host immune system are still unclear. In fact, evidence indicates that hMPV induces a poor innate immune response, thereby affecting the adaptive immunity. Among these mechanisms, is the promotion of an anergic state in T cells, instead of an effective polarization or activation, which could be induced by low levels of cytokine secretion. Further, the evidences support the notion that hMPV interferes with several pattern recognition receptors (PRRs) and cell signaling pathways triggered by interferon-associated genes. However, these mechanisms reported in hMPV are not like the ones reported for hRSV, as the latter has two non-structural proteins that are able to inhibit these pathways. Several reports suggest that viral glycoproteins, such as G and SH, could play immune-modulator roles during infection. In this work, we discuss the state of the art regarding the mechanisms that underlie the poor immunity elicited by hMPV. Importantly, these mechanisms will be compared with those elicited by other common respiratory viruses. © 2018 Frontiers Media S.A. All rights reserved.https://www.frontiersin.org/articles/10.3389/fimmu.2018.02466/ful

Evolución de la energía de fractura de dos hormigones resistentes a la acción de ciclos hielo-deshielo

The current standards that regulate use of structural concrete have highlighted the durability of concrete. However, how the fracture energy of concrete evolves under the action of freeze-thaw cycles is not well known. The fracture energy of two types of concrete, one with an air-entraining additive and the other with silica fume addition, is studied after four, 14 and 28 freeze-thaw cycles. The results obtained show that the concrete with an air-entraining additive was undamaged and that fracture energy grew slightly. In addition to this, they also showed that the concrete with silica fume addition suffered severe surface scaling and its fracture energy changed due to the greater fracture areas generated.La actual normativa que rige el empleo de hormigón estructural ha puesto enfásis en la durabilidad del hormigón. Sin embargo, no se conoce cómo evoluciona la energía de fractura del hormigón sometido a ciclos hielo- deshielo, lo cual es de vital importancia para asegurar la durabilidad y el correcto comportamiento mecánico de las estructuras de hormigón en entornos con heladas durante su vida útil. Se ha estudiado la evolución de la energía de fractura de un hormigón con aireante y de un hormigón con humo de sílice después de 4, 14 y 28 ciclos hielo-deshielo realizando ensayos de fractura. Los resultados muestran cómo el hormigón con aireante no sufre daño por los ciclos hielo-deshielo y cómo la energía de fractura del mismo aumenta ligeramente. El hormigón con humo de sílice se daña por los ciclos hielo-deshielo y reduce su energía de fractura al aumentar el area fracturada