3,374 research outputs found

    Comment on ‘On the dipole, velocity and acceleration forms in high-order harmonic generation from a single atom or molecule’

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    Authors acknowledge support from Spanish Ministerio de Ciencia e Innovacio ́n through the Consolider Program SAUUL (CSD2007-00013) and research project FIS2009-09522, from Junta de Castilla y Leo ́n through the Program for Groups of Excellence (GR27) and from the EC’s Seventh Framework Programme (LASERLAB-EUROPE, grant agreement no 228334)We show that the main conclusion of Baggesen and Madsen (2011 J. Phys. B: At. Mol. Opt. Phys. 44 115601) is not general but only valid in one dimension

    Critical analysis of the European Union directive which regulates the use of biofuels: An approach to the Spanish case

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    In recent times, the global debate on the environment has been centered on CO2 emissions. This gas is the major cause of the “greenhouse effect” and people are more concerned with the idea that the emissions of this gas should be minimized. As a result of this concern, the Kyoto Protocol was enacted and subscribed to by many countries, setting the maximum gas emissions for them. Fossil fuels are a major source of CO2 emissions. For some years now The European Union has been seeking to promote some years now the use of biofuels as substitutes for diesel or petrol for transport purposes. As a result of this policy, in 2003 the European Union (EU) Directive 2003/30/EC [1] was developed with the aim of promoting the use of biofuels as a substitute for diesel or gasoline among European Union countries as well as to contribute to fulfilling the commitments acquired on climate change, security of supply in environmentally friendly conditions and the promotion of renewable energy sources. In order to achieve these goals, the directive forces all EU members to ensure that before December 31 of 2010 at least 5.75% of all gasoline and diesel fuels sold for transport purposes are biofuels. European Union countries have social and economic characteristics unique to themselves. The energy dependence on foreign sources, the features of the agricultural sector or the degree of industrialization varies greatly from one country to another. In this context, it is questionable whether the obligation imposed by this directive is actually achieving in its application uniform and/or identical goals in each of the countries involved and whether the actions of the various governments are also aligned with these goals. All these ideas were developed in a previous report (Sobrino and Monroy (2009) [2]). This report examines the possibility of using hydrogen as an alternative to fossil fuels and biofuels from a technical, economic and environmental point of view in the specific case of a European Union country: Spain

    Valley in the efficiency of the high-order harmonic yield at ultra-high laser intensities

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    We study the process of high-order harmonic generation using laser pulses with non-adiabatic turn-on and intensities well above saturation. As a main point, we report the existence of a valley structure in the efficiency of single-atom high-order harmonic generation with increasing laser intensities. Consequently, after an initial decrease, the high-frequency radiation yield is shown to increase for higher intensities, returning to a level similar to the case below saturation. Such behavior contradicts the general belief of a progressive degradation of the harmonic emission at ultrahigh intensities, based on the experience with pulses with smoother turn-on. We shall show that this behavior corresponds to the emergence of a new pathway for high-order harmonic generation, which takes place during the pulse turn-on. Our study combines trajectory analysis, wavelet techniques and the numerical integration of 3-Dimensional Time Dependent Schrödinger Equation. The increase in efficiency raises the possibility of employing ultrahigh intensities to generate high-frequency radiation beyond the water window.Spanish Ministerio de Ciencia e Innovación through the Consolider Program SAUUL ( CSD2007-00013) and research project FIS2009-09522, from Junta de Castilla y León through the Program for Groups of Excellence (GR27) and from the EC’s Seventh Framework Programme ( LASERLAB-EUROPE, grant agreement n 228334)

    Analytical and experimental performance evaluation of BLE neighbor discovery process including non-idealities of real chipsets

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    The purpose of this paper is to evaluate from a real perspective the performance of Bluetooth Low Energy (BLE) as a technology that enables fast and reliable discovery of a large number of users/devices in a short period of time. The BLE standard specifies a wide range of configurable parameter values that determine the discovery process and need to be set according to the particular application requirements. Many previous works have been addressed to investigate the discovery process through analytical and simulation models, according to the ideal specification of the standard. However, measurements show that additional scanning gaps appear in the scanning process, which reduce the discovery capabilities. These gaps have been identified in all of the analyzed devices and respond to both regular patterns and variable events associated with the decoding process. We have demonstrated that these non-idealities, which are not taken into account in other studies, have a severe impact on the discovery process performance. Extensive performance evaluation for a varying number of devices and feasible parameter combinations has been done by comparing simulations and experimental measurements. This work also includes a simple mathematical model that closely matches both the standard implementation and the different chipset peculiarities for any possible parameter value specified in the standard and for any number of simultaneous advertising devices under scanner coverage

    Evaluación de algunos aspectos de la biocompatibilidad de biomateriales in vitro

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    Los biomateriales para uso médico se han ido desarrollando de acuerdo a los avances en los campos de la medicina, bioquímica, farmacia y las ciencias de los materiales. Estos deben ser biocompatibles, por eso es necesario desarrollar un grupo de ensayos biológicos encaminados a este fin. Las pruebas de citotoxicidad in vitro tienen aplicabilidad general y uso extensamente difundido en la evaluación de un amplio rango de materiales. Se ha encontrado cierta relación entre la citotoxicidad no específica del biomaterial in vitro y su efecto irritante in vivo. En nuestro laboratorio se aplicó el método descrito por Stanley HR (1985) para la evaluación toxicológica de biomateriales, habiéndose evaluado hasta la fecha diferentes materiales obtenidos en el Centro de Biomateriales de la Universidad de La Habana, entre ellos: el obturante dental Obtudent Fotocurado (FC), el sellante dental Cubridem Autocurado (AC), el adhesivo tisular Tisuacryl y los cementos óseos Biograft-G y Apafill-G. El Obtudent FC resultó citotóxico, sin embargo su citotoxicidad se encontró en el rango de la de sus análogos comerciales. La citotoxicidad del Cubridem AC y del Tisuacryl no se diferenció significativamente de los niveles encontrados para sus controles comerciales, al igual que el Biograft-G, aunque en este caso el resultado fue ligeramente citotóxico según la clasificación de Stanley. El Apafill-G no resultó citotóxico.Peer Reviewe

    Weighted LpL^p-boundedness of Fourier series with respect to generalized Jacobi weights

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    Let w be a generalized Jacobi weight on the interval [-1,1] and, for each function f, let Snf denote the n-th partial sum of the Fourier series of f in the orthogonal polynomials associated to w. We prove a result about uniform boundedness of the operators Sn in some weighted Lp spaces. The study of the norms of the kernels Kn related to the operators Sn allows us to obtain a relation between the Fourier series with respect to different generalized Jacobi weights

    Mandibular ameloblastoma. A review of the literature and presentation of six cases

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    El ameloblastoma es un tumor odontogénico benigno de origen epitelial sin inducción en el tejido conectivo. En el tratamiento del mismo se debe valorar el tipo clínico (sólido y multiquístico, uniquístico, periférico), la localización y el tamaño del tumor, así como la edad del paciente. Recientemente se han publicado algunos artículos con el fin de actualizar los conocimientos y actitudes terapéuticas frente al ameloblastoma. Se presentan seis casos de pacientes afectos de ameloblastomas localizados en la mandíbula, tratados en los últimos siete años. Se aportan datos acerca de su aparición clínica, sus características histológicas, el manejo terapéutico realizado que consistió en la extirpación de la lesión, fresado perilesional del hueso o resección en bloque, según el tipo de ameloblastoma. Finalmente analizamos el seguimiento y la aparición de recidivas en los pacientes presentados. El objetivo de este artículo es revisar los conceptos respecto al ameloblastoma que se han publicado recientemente y valorar su influencia en la actitud del clínico a la hora de actuar frente a esta patología, tomando como punto de partida para ilustrar está discusión la presentación de nuestra experiencia respectoal ameloblastoma.Ameloblastoma is a benign odontogenic tumour of epithelial origin without induction in the connective tissue. In treating this type of tumour, it is important to assess the clinical type (solid, multicystic, unicystic, peripheral), localisation, and size of the tumour as well as age of the patient. Articles have recently been published with the purpose of providing updated knowledge and therapeutic approaches to ameloblastoma. We present six cases of patients with localised mandibular ameloblastoma who were treated during the last seven years. We present data on clinical appearance, histological characteristics, and therapeutic approach that was used, which included excision of the lesion, perilesional drilling of the bone, or block resection, according to the type of ameloblastoma. Lastly, we analysed follow-up measures and the rate of recurrence in these patients. The aim of this paper is to review the concepts relating to ameloblastoma that have been published recently and to assess their influence on the clinical attitude taken when facing this pathology, using our experience with ameloblastoma as a starting point to illu strate this discussion

    SAGT: Aplicación informática para análisis de generalizabilidad

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    Se presenta un nuevo software para realizar análisis de generalizabilidad. Las características del mismo superan las limitaciones de programas anteriores (GENOVA, TG o EduG), tanto a nivel de tratamiento numérico como gráfico y en la importación/exportación de datos. El entorno del programa es más amigable. Para demostrar su eficacia se utiliza en el análisis de datos y valoración de resultados de un programa de intervención para la reducción de discriminación de género en las clases de educación física (EF). Se utiliza un diseño observacional y un diseño de generalizabilidad ortogonal con 6 facetas parcialmente anidado. El programa se desarrolla durante seis meses. La muestra está compuesta por 100 alumnos (51 chicas y 49 chicos) con edades comprendidas entre los 10 y los 12 años que cursaban 5º de Educación Primaria y se encontraban distribuidos en cuatro grupos. Los resultados del anàlisis de generalizabilidad señalan que la herramienta de observación es fiable, válida y precisa y que los observadores son altamente fiables (k = 0.73-0.81, G = 1). El ANOVA realizado señala que el programa de intervención ha sido eficaz. Además, se ha demostrado la eficacia y usabilidad del programa SAGT
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