A contour matching approach for accurate NOAA-AVHRR image navigation

Although different methods for NOAA AVHRR image navigation have already been established, the multitemporal and multi-satellite character of most studies requires automatic and accurate methods for navigation of satellite images. In the proposed method, a simple Kepplerian orbital model for the NOAA satellites is considered as reference model, and mean orbital elements are given as input to the model from ephemeris data. In order to correct the errors caused by these simplifications, errors resulting from inaccuracies in the positioning of the satellite and failures in the satellite internal clock, an automatic global contour matching approach has been adopted. First, the sensed image is preprocessed to obtain a gradient energy map of the reliable areas (sea-land contours) using a cloud detection algorithm and a morphological gradient operator. An initial estimation of the reliable contour positions is automatically obtained. The final positions of the contours are obtained by means of an iterative local minimization procedure that allows a contour to converge on an area of high image energy (edge). Global transformation parameters are estimated based on the initial and final positions of all reliable contour points. Finally, the performance of this approach is assessed using NOAA 14 AVHRR images from different geographic areas.Postprint (published version

Organocatalyzed Enantioselective Aldol and Henry Reactions Starting from Benzylic Alcohols

Pioneering aldol and Henry reactions starting from benzylic-type alcohols are described. The aldol reaction has been successfully performed following a one-pot strategy starting from alcohols, while the Henry reaction has been carried out following a sequential protocol for the first time. In both processes, enantiomerically enriched products were obtained with good yields and high enantioselectivities. We have also demonstrated that in reactions sensitive to small amounts of acid the use of alcohols instead of aldehydes could be a good solution for improving the results of these reactions. (Figure presented.)

Phase-transitions in spin-crossover thin films probed by graphene transport measurements

Future multi-functional hybrid devices might combine switchable molecules and 2D material-based devices. Spin-crossover compounds are of particular interest in this context since they exhibit bistability and memory effects at room temperature while responding to numerous external stimuli. Atomically-thin 2D materials such as graphene attract a lot of attention for their fascinating electrical, optical, and mechanical properties, but also for their reliability for room-temperature operations. Here, we demonstrate that thermally-induced spin-state switching of spin-crossover nanoparticle thin films can be monitored through the electrical transport properties of graphene lying underneath the films. Model calculations indicate that the charge carrier scattering mechanism in graphene is sensitive to the spin-state dependence of the relative dielectric constants of the spin-crossover nanoparticles. This graphene sensor approach can be applied to a wide class of (molecular) systems with tunable electronic polarizabilities.Comment: main text: 13 pages, 5 figures ; SI: 14 pages, 12 figure

Usos académicos y sociales de las tecnologías digitales del estudiante universitario de primer año

Esta comunicación tiene como objetivo comprender cómo los estudiantes universitarios de primer año utilizan la tecnología digital para fines académicos y sociales. Los resultados nos permiten concluir que la mayoría de los estudiantes se sientan cómodos con las tecnologías digitales y ven las redes sociales como un medio de conexión e interacción con amigos más con fines sociales que académicos. Los estudiantes suelen preferir el correo electrónico personal, la interacción cara a cara, las redes sociales y los teléfonos móviles para comunicarse y conectarse con otros. Sobre los hábitos de estudio, los estudiantes prefieren aprender por sí mismos, trabajar independientemente y estudiar en casa. Esto contradice uno de los argumentos sobre las Generación Net que dice que los estudiantes de hoy están a favor del enfoque del trabajo colaborativo.This paper aims to provide some important insights into how first-year university students use digital technology for academic and social purposes. We conclude that most students feel comfortable with digital technologies and they see social networks as more about connecting and interacting with friends than for academic communication. Results show that students generally prefer personal email, face-to-face interaction, social networks and mobile phones to communicate and connect with others. Regarding study habits, students prefer to learn by themselves, work independently and to study at home. This contradicts one of the net generation claims which says students today favor collaborative approaches

Vortex solutions in the noncommutative torus

Vortex configurations in the two-dimensional torus are considered in noncommutative space. We analyze the BPS equations of the Abelian Higgs model. Numerical solutions are constructed for the self-dual and anti-self dual cases by extending an algorithm originally developed for ordinary commutative space. We work within the Fock space approach to noncommutative theories and the Moyal-Weyl connection is used in the final stage to express the solutions in configuration space.Comment: 18 pages, 5 figure

The quantum paraelectric behavior of SrTiO_{3} revisited: relevance of the structural phase transition temperature

It has been known for a long time that the low temperature behavior shown by the dielectric constant of quantum paraelectric $SrTiO_{3}$ can not be fitted properly by Barrett's formula using a single zero point energy or saturation temperature ($T_{1}$). As it was originally shown [K. A. M\"{u}ller and H. Burkard, Phys. Rev. B {\bf 19}, 3593 (1979)] a crossover between two different saturation temperatures ($T_{1l}$=77.8K and $T_{1h}$=80K) at $T\sim10K$ is needed to explain the low and high temperature behavior of the dielectric constant. However, the physical reason for the crossover between these two particular values of the saturation temperature at $T\sim10K$ is unknown. In this work we show that the crossover between these two values of the saturation temperature at $T\sim10K$ can be taken as a direct consequence of (i) the quantum distribution of frequencies $g(\Omega)\propto\Omega^{2}$ associated with the complete set of low-lying modes and (ii) the existence of a definite maximum phonon frequency given by the structural transition critical temperature $T_{tr}$.Comment: 8 pages, 3 figure

Functionalization of p-activated alcohols by trapping carbocations in pure water under smooth conditions

Acetic acid as catalyst in pure water was found to be an excellent reaction medium for the direct dehydrative functionalization of p-activated alcohols using a wide variety of interesting C-, P-, and S-centered nucleophiles, such as indoles, pyrrole, anilines, 1, 3-dicarbonyl compounds, diphenyl phosphite and pyridine-2-thiol. The smooth reaction conditions, along with high yields, short reaction times, clean reaction crudes, an easy product isolation procedure, plus the reusability of the catalyst and the use of no excess of nucleophiles, make this approach an atom economical, green and appealing method to efficiently trap carbocations in pure water, leading to new Csp3 X bonds (X = Csp2, Csp3, P and S)

Prevenció de la conducta pertorbadora en el context escolar

CuestionarioRed de Universidades con Carreras en Informática (RedUNCI