Admissibility condition for exceptional Laguerre polynomials

We prove a necessary and sufficient condition for the integrability of the weight associated to the exceptional Laguerre polynomials. This condition is very much related to the fact that the associated second order differential operator has no singularities in $(0,+\infty)$.Comment: 12 page

El problema del coste en la industria hotelera: el servicio de alojamiento

La innegable importancia del sector turístico en nuestro país reclama, en nuestra opinión, un riguroso estudio de los diversos componentes que configuran su oferta final, dentro de la que, sin ningún género de duda, ocupa una importancia destacada la industria hotelera. Ello otorga especial relevancia a todo intento de definición y cálculo de los costes que inciden en la misma, y en particular los servicios de restauración y alojamiento, del último de los cuales nos ocupamos en el presente trabajo.We think that the great importance of tourism bussiness in our country makes necessary the elaboration of a deep study about the different factors that shape the completed offer in the sector. The products dealing with accommodations are undoubtedly an important part within this offer. It involves a special meaning for any attempt to define this sort of products and to calculate the costs that affect them. These last aspects we treat in the present piece of work

Does grade retention affect achievement? Some evidence from PISA

Grade retention practices are at the forefront of the educational debate. In this paper, we use PISA 2009 data for Spain to measure the effect of grade retention on students achievement. One important problem when analyzing this question is that school outcomes and the propensity to repeat a grade are likely to be determined simultaneously. We address this problem by estimating a Switching Regression Model. We …find that grade retention has a negative impact on educational outcomes, but we confi…rm the importance of endogenous selection, which makes observed differences between repeaters and non-repeaters appear 14.6% lower than they actually are. The effect on PISA scores of repeating is much smaller (-10% of non-repeaters average) than the counterfactual reduction that non-repeaters would suffer had they been retained as repeaters (-24% of their average). Furthermore, those who repeated a grade during primary education suffered more than those who repeated a grade of secondary school, although the effect of repeating at both times is, as expected, much larger.Grade retention, educational scores, PISA

Does grade retention affect achievement? Some evidence from Pisa

Grade retention practices are at the forefront of the educational debate. In this paper, we use PISA 2009 data for Spain to measure the effect of grade retention on students’achievement. One important problem when analyzing this question is that school outcomes and the propensity to repeat a grade are likely to be determined simultaneously. We address this problem by estimating a Switching Regression Model. We find that grade retention has a negative impact on educational outcomes, but we confirm the importance of endogenous selection, which makes observed differences between repeaters and non-repeaters appear 14.6% lower than they actually are. The effect on PISA scores of repeating is much smaller (-10% of non-repeaters’average) than the counterfactual reduction that non-repeaters would suffer had they been retained as repeaters (-24% of their average). Furthermore, those who repeated a grade during primary education suffered more than those who repeated a grade of secondary school, although the effect of repeating at both times is, as expected, much larger.Grade retention, educational scores, PISA

Mechanism of Alkyl Migration in Diorganomagnesium 2,6-Bis(imino)pyridine Complexes: Formation of Grignard-Type Complexes with Square-Planar Mg(II) Centers

Dialkylmagnesium compounds [MgR2L2] (R = n-Bu, L = none or R = Bn, L = THF) react with 2,6-bis(imino)pyridines (BIP) to afford different types of Mg(II) alkyl complexes, depending on the nature of R. For R = n-Bu, thermally stable products resulting from selective alkyl transfer to the pyridine nitrogen (N1) atom are obtained. However, NMR studies showed that the reaction of [Mg(Bn)2THF2] with iPrBIP at −65 °C leads to a thermally unstable product arising from benzyl migration to position C2 in the pyridine ring. Above +5 °C, this compound rearranges, cleanly yielding a mixture of two isomeric complexes, in which the benzyl group has migrated to positions C3 or C4 of the central ring, respectively. Similar isomeric mixtures were obtained when [Mg(Bn)2THF2] was reacted with iPrBIP or MesBIP at room temperature. Such mixtures are thermally stable below 80 °C, but at this temperature, the 3-benzyl isomer converts into the thermodynamically favored 4-benzyl product, albeit not quantitatively. An alternate route was devised for the selective syntheses of the latter type of compounds. The X-ray diffraction structure of one of them provided an unusual example of a square-planar alkylmagnesium(II) center.Ministerio de Economía e Innovación CTQ2015-68978-

Presencia y edad de vulcaniras en el Jurásico del Norte de Valencia (Cordillera Ibérica, España)

Se da cuenta en este trabajo de la presencia de rocas volcánicas, intercaladas en las series carbonatadas del Jurásico del norte de la provincia de Valencia (región de Alcublas), cuya edad ha podido ser determinada como Bajociense inferior. El hecho de que exista vulcanismo de edad similar en gran parte de las codilleras Béticas(subbético), sugiere la existencia de una fase de distensión con marcada amplitud durante los primeros tiempos del Jurásico medio. Por otra parte, las posibles emanaciones de sílice, acompañadas del proceso volcánico, pudieron ser unas de las causantes principales de la presencia ide nódulos de sílex en el Bajociense de una amplia región.Peer reviewe

SRec, software de animación de la recursividad

SRec es una aplicación que permite la generación automatizada de animaciones de programas basados en la recursividad. Ofrece una gran variedad de facilidades educativas como cargar y guardar animaciones ya generadas, configuración de la información que se muestra en cada momento y una interfaz muy intuitiva. Mitiga el esfuerzo de elaboración de animaciones para los profesores y ayuda a analizar los algoritmos recursivos a los alumnos. Los resultados obtenidos de su utilización en las clases indican una gran aceptación por parte de los alumnos y una mejora en sus evaluaciones académicas.Peer Reviewe

Oxygen-Induced Dimerization of Alkyl-Manganese(II) 2,6-Bisiminopyridine Complexes: Selective Synthesis of a New Ditopic NNN-Pincer Ligand

The outcome of the reaction of manganese(II) dialkyls with 2,6-bisiminopyridine (BIP) ligands is dramatically altered by the presence of very small amounts of oxygen (< 0.5 mol %), leading to binuclear species. These arise from the dimerization of the initial product, a Mn(II) 4-alkyl-2,6-bisiminodihydropyridinate alkyl complex. Cleavage of the binuclear Mn products with methanol affords the free dimeric bases, which can be regarded as a special type of ditopic NNN pincer ligand with an unusual tricyclic framework. The coordinative ability of the new ligands has been probed with the syntheses of Zn and Pd organometallic derivativesMinisterio de Economía e Innovación TQ2015- 68978-

Performance Study of Software AER-Based Convolutions on a Parallel Supercomputer

This paper is based on the simulation of a convolution model for bioinspired neuromorphic systems using the Address-Event-Representation (AER) philosophy and implemented in the supercomputer CRS of the University of Cadiz (UCA). In this work we improve the runtime of the simulation, by dividing an image into smaller parts before AER convolution and running each operation in a node of the cluster. This research involves a test cases design in which the optimal parameters are set to run the AER convolution in parallel processors. These cases consist on running the convolution taking an image divided in different number of parts, applying to each part a Sobel filter for edge detection, and based on the AER-TOOL simulator. Execution times are compared for all cases and the optimal configuration of the system is discussed. In general, CRS obtain better performances when the image is divided than for the whole image.Ministerio de Ciencia e Innovación TEC2009-10639-C04-0