Generalized Jacobi–Weierstrass operators and Jacobi expansions

We present a realization for some K-functionals associated with Jacobi expansions in terms of generalized Jacobi–Weierstrass operators. Fractional powers of the operators as well as results concerning simultaneous approximation and Nikolskii–Stechkin type inequalities are also considered

Estimación de la superficie quemada en los incendios forestales de Canarias en 2007 utilizando sinérgicamente imágenes MODIS y anomalías térmicas

El presente trabajo plantea una metodología rápida, precisa y económica para la estimación del área quemada en los incendios forestales utilizando técnicas de teledetección. El algoritmo utilizado se basa en la determinación o establecimiento de umbrales a partir de la banda del infrarrojo cercano. Se han utilizados los productos de reflectancia MODIS y las series temporales de anomalías térmicas proporcionadas por la NASA. Dicho umbral que separa área quemada de noquemada se ha basado en la búsqueda de la máxima coincidencia entre área quemada definida por la banda del infrarrojo cercano y zona de influencia de las anomalías térmicas. Los resultados muestran la utilidad de la metodología propuesta para la estimación de áreas quemadas y su importancia a la hora de localizar de una forma rápida las zonas de intervención prioritaria, así como para la planificación de futuros trabajos de restauración de la zona afectada

Enantio- and Diastereoselective Nucleophilic Addition of N-tert-Butylhydrazones to Isoquinolinium Ions through Anion-Binding Catalysis

A highly enantio- and diastereoselective thiourea-catalyzed dearomatization of isoquinolines employing N-tert-butylhydrazones as neutral alpha-azo carbanions and masked acyl anion equivalents has been developed. Experimental and computational data supports the generation of highly ordered complexes wherein the chloride behaves as a template for the catalyst, the hydrazone reagent, and the isoquinolinium cation, providing excellent stereocontrol in the formation of two contiguous stereogenic centers. The ensuing selective and high-yielding transformations provide appealing dihydroisoquinoline derivatives

Implementation of a harvest control rule for northern Atlantic albacore

A Harvest Control Rule was developed for North Atlantic albacore during the 2013 assessment, this paper documents the procedure used.Versión del edito

Hydrological heterogeneity in Mediterranean reclaimed slopes: runoff and sediment yield at the patch and slope scales along a gradient of overland flow

Hydrological heterogeneity is recognized as a fundamental ecosystem attribute in drylands controlling the flux of water and energy through landscapes. Therefore, mosaics of runoff and sediment source patches and sinks are frequently identified in these dry environments. There is a remarkable scarcity of studies about hydrological spatial heterogeneity in restored slopes, where ecological succession and overland flow are interacting. We conducted field research to study the hydrological role of patches and slopes along an "overland flow gradient" (gradient of overland flow routing through the slopes caused by different amounts of run-on coming from upslope) in three reclaimed mining slopes of Mediterranean-continental climate. We found that runoff generation and routing in non-rilled slopes showed a pattern of source and sink areas of runoff. Such hydrological microenvironments were associated with seven vegetation patches (characterized by plant community types and cover). Two types of sink patches were identified: shrub Genista scorpius patches could be considered as "deep sinks", while patches where the graminoids Brachypodium retusum and Lolium perenne dominate were classified as "surface sinks" or "runoff splays". A variety of source patches were also identified spanning from "extreme sources" (Medicago sativa patches; equivalent to bare soil) to "poor sources" (areas scattered by dwarf-shrubs of Thymus vulgaris or herbaceous tussocks of Dactylis glomerata). Finally, we identified the volume of overland flow routing along the slope as a major controlling factor of "hydrological diversity" (heterogeneity of hydrological behaviours quantified as Shannon diversity index): when overland flow increases at the slope scale hydrological diversity diminishes

Structural and functional control of surface-patch to hillslope runoff and sediment connectivity in Mediterranean dry reclaimed slope systems

Connectivity has emerged as a useful concept for exploring the movement of water and sediments between landscape locations and across spatial scales. In this study, we examine the structural and functional controls of surfacepatch to hillslope runoff and sediment connectivity in three Mediterranean dry reclaimed mining slope systems that have different long-term development levels of vegetation and rill networks. Structural connectivity was assessed using flow path analysis of coupled vegetation distribution and surface topography, providing field indicators of the extent to which surface patches that facilitate runoff and sediment production are physically linked to one another in the studied hillslopes. Functional connectivity was calculated using the ratio of patch-scale to hillslope-scale observations of runoff and sediment yield for 21 monitored hydrologically active rainfall events. The impact of the dynamic interactions between rainfall conditions and structural connectivity on functional connectivity were further analysed using general linear models with a backward model structure selection approach. Functional runoff connectivity during precipitation events was found to be dynamically controlled by antecedent precipitation conditions and rainfall intensity and strongly modulated by the structural connectivity of the slopes. On slopes without rills, both runoff and sediments for all events were largely redistributed within the analysed hillslopes, resulting in low functional connectivity. Sediment connectivity increased with rainfall intensity, particularly in the presence of rill networks where active incision under high-intensity storm conditions led to large non-linear increases in sediment yield from the surface-patch to the hillslope scales. Overall, our results demonstrate the usefulness of applying structuraland functional-connectivity metrics for practical applications and for assessing the complex links and controlling factors that regulate the transference of both surface water and sediments across different landscape scales

Comparing AWiFS and MERIS images for land use – land cover mapping in Spain

As global land use – land cover mapping has become of great importance, an evaluation of the benefits and disadvantages of using satellite data with either increased spatial or spectral resolution would be adequate for the improvement of methodologies. This paper describes the comparison of AWiFS (Advanced Wide Field Sensor) and MERIS-FR (MEdium Resolution Imaging Spectrometer – Full Resolution) -based classifications of the Spanish province of Madrid. Maximum Likelihood Supervised Classification was performed using training areas based on data coming from the Spanish National Forest Inventory and from the CORINE Land Cover 2000 data bases. The classification process with AWiFS was more laborious than with MERIS-FR but the overall accuracy could be increased by 10%. For some surfaces such as deciduous forests, the high spectral resolution of MERIS-FR might be an advantage. Researchers will have to decide if the better results obtained with AWiFS compensate for the higher cost of the images and the more effortful processing. Dada la creciente importancia de los mapas de usos y coberturas, se considera de gran utilidad el realizar una evaluación de los beneficios y desventajas del uso de imágenes de satélite de mejor resolución espacial o espectral, de cara a la mejora de ciertas metodologías. En este trabajo se presenta la comparación de clasificaciones de la provincia de Madrid (España) realizadas a partir de imágenes AWiFS (Advanced Wide Field Sensor) y MERIS-FR (MEdium Resolution Imaging Spectrometer – Full Resolution). El algoritmo de clasificación empleado fue el de máxima probabilidad para lo que se usaron áreas de entrenamiento basadas en datos procedentes del Inventario Forestal Nacional y del CORINE Land Cover 2000. La clasificación a partir de la imagen AWiFS fue más laboriosa obteniéndose una precisión global un 10% mayor que en el caso de MERIS-FR. Sin embargo, para ciertas clases como la de bosque caducifolio, la mejor resolución espectral de MERIS-FR supuso una ventaja. Queda en mano de los investigadores decidir si los mejore resultados obtenidos con AWiFS compensan el mayor coste de las imágenes y el mayor esfuerzo de procesado

Cyclotron effective masses in layered metals

Many layered metals such as quasi-two-dimensional organic molecular crystals show properties consistent with a Fermi liquid description at low temperatures. The effective masses extracted from the temperature dependence of the magnetic oscillations observed in these materials are in the range, m^*_c/m_e \sim 1-7, suggesting that these systems are strongly correlated. However, the ratio m^*_c/m_e contains both the renormalization due to the electron-electron interaction and the periodic potential of the lattice. We show that for any quasi-two-dimensional band structure, the cyclotron mass is proportional to the density of states at the Fermi energy. Due to Luttinger's theorem, this result is also valid in the presence of interactions. We then evaluate m_c for several model band structures for the \beta, \kappa, and \theta families of (BEDT-TTF)_2X, where BEDT-TTF is bis-(ethylenedithia-tetrathiafulvalene) and X is an anion. We find that for \kappa-(BEDT-TTF)_2X, the cyclotron mass of the \beta-orbit, m^{*\beta}_c, is close to 2 m^{*\alpha}_c, where m^{*\alpha}_c is the effective mass of the \alpha- orbit. This result is fairly insensitive to the band structure details. For a wide range of materials we compare values of the cyclotron mass deduced from band structure calculations to values deduced from measurements of magnetic oscillations and the specific heat coefficient.Comment: 12 pages, 3 eps figure

Geometric aspects of nonholonomic field theories

A geometric model for nonholonomic Lagrangian field theory is studied. The multisymplectic approach to such a theory as well as the corresponding Cauchy formalism are discussed. It is shown that in both formulations, the relevant equations for the constrained system can be recovered by a suitable projection of the equations for the underlying free (i.e. unconstrained) Lagrangian system.Comment: 29 pages; typos remove

Wide band-gap tuning Cu2ZnSn1-xGexS4 single crystals: Optical and vibrational properties

The linear optical properties of Cu2ZnSn1-xGe x S4 high quality single crystals with a wide range of Ge contents (x=0.1, 0.3, 0.5, 0.7, 0.9 and 1) have been investigated in the ultraviolet and near infrared range using spectroscopic ellipsometry measurements. From the analysis of the complex dielectric function spectra it has been found that the bandgap E 0 increases continuously from 1.49eV to 2.25eV with the Ge content. Furthermore, the evolution of the interband transitions E 1A and E 1B has been also determined. Raman scattering using three different excitation wavelengths and its analysis have been performed to confirm the absence of secondary phases in the samples, and to distinguish between stannite, wurtzite, wurzstannite and kesterite structures. Additionally, the analysis of the high resolution Raman spectra obtained in samples with different [Ge]/([Ge]+[Sn]) ratios allows describing a bimodal behavior of the dominant A modes. The understanding of the incorporation of Ge into the Cu2ZnSnS4 lattice is fundamental in order to develop efficient bandgap engineering of these compounds towards the fabrication of kesterite based solar cells with enhanced performanceThis work was supported by the Marie Curie-ITN project (KESTCELL, GA: 316488), Marie Curie-IRSES project (PVICOKEST, GA: 269167), AMALIE (TEC2012-38901-C02-01) and SUNBEAM (ENE2013-49136-C4-3-R) project funded by the Spanish Ministry of Economy and Competitiveness. RC acknowledges financial support from Spanish MINECO within the Ramón y Cajal program (RYC-2011-08521