Polivalencia fitoclimática y diversidad potencial de cubiertas forestales arbóreas naturales en la España peninsular

A multivariate methodology was assayed to evaluate the phytoclimatic versatility of peninsular Spain and how this relates to the potential diversity of natural tree covers. The instances of greatest phytoclimatic versatility occur in a range of altitude between 1000 and 1300 m; these are cool phytoclimates with only short, low-intensity periods of aridity. These factorial ambits of maximum versatility correspond chiefly to the substeppe nemoral subtype 6(7), followed by genuine nemoral VI and humid nemoromediterranean 6(4)2 subtypes. The lowest values of versatility and potential diversity correspond to dry genuine Mediterranean (4i) or transitional Mediterranean 4(6)1 subtypes and to alpine oroborealoid or oroarcticoid subtypes. In geographical terms, intermediate mountain areas in the north of the Peninsula and some massifs in the southern half score the highest in the Diversity Index used. The lowest scores are found in the southern half of the Peninsula, although in the northern half low scores are also found for littoral areas, interior areas of the Duero and Ebro basins and alpine areas. Autoecological phytoclimatic spectra headed by stands of Pinus nigra and Quercus petraea present the greatest phytoclimatic versatility, while those headed by Quercus ilex ballota and Pinus uncinata stands present the least versatility. This article offers new methodological horizons for the study of the effects of climate change on plant diversity.Se ensaya una metodología multivariante de evaluación de la polivalencia fitoclimática de la España peninsular y de su relación con la diversidad potencial de las cubiertas arbóreas naturales. Las mayores polivalencias fitoclimáticas se dan en una franja altitudinal situada entre los 1000 y los 1.300 m, correspondiendo a ámbitos fitoclimáticos frescos y con escasa duración e intensidad de la aridez. Estos ámbitos factoriales de máxima polivalencia se corresponden principalmente con el subtipo nemoral subestepario 6(7), seguido del nemoral genuino 6 y del nemoromediterráneo húmedo 6(4)2. Los menores valores de polivalencia y de diversidad potencial se corresponden con subtipos mediterráneos genuinos (4i) o transicionales 4(6)1 secos y con subtipos oroborealoides u oroarticoides de alta montaña. Desde un punto de vista geográfico, las zonas de media montaña de la mitad norte peninsular y algunos macizos montañosos de la mitad sur dan los valores más altos del Índice de Diversidad utilizado, mientras que los menores se dan en la mitad sur peninsular, aunque en la mitad norte las áreas litorales, las áreas interiores de las cuencas del Duero y Ebro así como y en las áreas de alta montaña también se corresponden con valores bajos del índice. Los espectros fitoclimáticos de carácter autoecológico encabezados por pinares de Pinus nigra y por robledales de Quercus petraea presentan la mayor polivalencia fitoclimática, mientras que los encabezados por encinares de Quercus ilex ballota y por pinares de Pinus uncinata presentan la menor. El presente trabajo abre nuevos horizontes metodológicos para el estudio de los efectos del cambio climático sobre la diversidad vegetal

A language for real time simulation of processes with boolean inputs and outputs

This paper deals with the problem of real time simulation of processes with boolean inputs and outputs. A language for this purpose and the programs that processes it is presented. The language allows the description of processes with simultaneous evolutions as a timed petri net type of description is used. Random failures can also be Introduced in the behaviour of the model. The language allows the control of a semlgraphic CRT in order to facilitate the task of following the model behaviour

Monte Carlo simulations of post-common-envelope white dwarf + main sequence binaries: The effects of including recombination energy

Detached WD+MS PCEBs are perhaps the most suitable objects for testing predictions of close-compact binary-star evolution theories, in particular, CE evolution. The population of WD+MS PCEBs has been simulated by several authors in the past and compared with observations. However, most of those predictions did not take the possible contributions to the envelope ejection from additional sources of energy (mostly recombination energy) into account. Here we update existing binary population models of WD+MS PCEBs by assuming that a fraction of the recombination energy available within the envelope contributes to ejecting the envelope. We performed Monte Carlo simulations of 10^7 MS+MS binaries for 9 different models using standard assumptions for the initial primary mass function, binary separations, and initial-mass-ratio distribution and evolved these systems using the publicly available BSE code. Including a fraction of recombination energy leads to a clear prediction of a large number of long orbital period (>~10 days) systems mostly containing high-mass WDs. The fraction of systems with He-core WD primaries increases with the CE efficiency and the existence of very low-mass He WDs is only predicted for high values of the CE efficiency (>~0.5). All models predict on average longer orbital periods for PCEBs containing C/O-core WDs than for PCEBs containing He WDs. This effect increases with increasing values of both efficiencies. Longer periods after the CE phase are also predicted for systems containing more massive secondary stars. The initial-mass-ratio distribution affects the distribution of orbital periods, especially the distribution of secondary star masses. Our simulations, in combination with a large and homogeneous observational sample, can provide constraints on the values of the CE efficiencies, as well as on the initial-mass-ratio distribution for MS+MS binary stars.Comment: 11 pages, 10 figures, accepted for publication in A&

Comparative Analysis of Extrusion Processes by Finite Element Analysis

AbstractExtrusion processes are quite extended in the manufacturing of long products for a wide range of industrial applications. There are different approaches of extrusion processes, depending on either the final shape of the product to obtain or the maximum loading capacity of the equipment to be used. This work presents a comparative study of extrusion processes (solid and cup extrusion), considering both direct and indirect forming conditions and showing the most interesting differences between them. The comparison is realized by Finite Element simulation of the processes, using the code DEFORM F2. The material is a low carbon steel (AISI-1010) and the same extrusion ratio and ram displacement are considered in all cases. By comparing the required forces it can be concluded that required loads are higher in cup extrusion processes than in solid extrusion ones. Regarding the friction load, the maximum contribution due to the die-billet contact in cup extrusion is much higher than in the case of solid extrusion. On the contrary, the maximum friction load contribution due to the container wall is much higher in the case of solid extrusion than in cup extrusion

Synthesis and complementary self-association of novel lipophilic π-conjugated nucleoside oligomers

The following article appeared in Organic and Biomolecular Chemistry 13.15 (2015): 4506-4513 and may be found at http://dx.doi.org/10.1039/c5ob00098j, reproduced by permission of The Royal Society of ChemistryA series of lipophilic nucleosides comprising natural and non-natural bases that are π-conjugated to a short oligophenylene-ethynylene fragment has been synthesized. These bases comprise guanosine, isoguanosine, and 2-aminoadenosine as purine heterocycles, and cytidine, isocytosine and uridine as complementary pyrimidine bases. The hydrogen-bonding dimerization and association processes between complementary bases were also studied by 1H NMR and absorption spectroscopy in order to obtain the relevant association constantsFunding from the European Research Council (ERC-StG 279548) and MINECO (CTQ2011-23659) is gratefully acknowledge

Retrieving leaf area index from multi-angular airborne data

This work is aimed to demonstrate the feasibility of a methodology for retrieving bio-geophysical variables whilst at the same time fully accounting for additional information on directional anisotropy. A model-based approach has been developed to deconvolve the angular reflectance into single landcovers reflectances, attempting to solve the inconsistencies of 1D models and linear mixture approaches. The model combines the geometric optics of large scale canopy structure with principles of radiative transfer for volume scattering within individual crowns. The reliability of the model approach to retrieve LAI has been demonstrated using data from DAISEX- 99 campaign at Barrax, Spain. Airborne data include POLDER and HyMap data in which various field plots were observed under varying viewing/illumination angles. Nearly simultaneously, a comprehensive field data set was acquired on specific crop plots. The inversions provided accurate LAI values, revealing the model potential to combine spectral and directional information to increase the likely accuracy of the retrievals. In addition, the sensitivity of retrievals with the angular and spectral subset of observations was analysed, showing a high consistency between results. This study has contributed to assess the uncertainties with products derived from satellite data like SEVIRI/MSG

The contribution of oxygen-neon white dwarfs to the MACHO content of the Galactic halo

Context. The interpretation of microlensing results towards the Large Magellanic Cloud (LMC) still remains controversial. White dwarfs have been proposed to explain these results and, hence, to contribute significantly to the mass budget of our Galaxy. However, several constraints on the role played by regular carbon-oxygen white dwarfs exist. Aims. Massive white dwarfs are thought to be made of a mixture of oxygen and neon. Correspondingly, their cooling rate is larger than those of typical carbon-oxygen white dwarfs and they fade to invisibility in short timescales. Consequently, they constitute a good candidate for explaining the microlensing results. Methods. Here, we examine in detail this hypothesis by using the most recent and up-to-date cooling tracks for massive white dwarfs and a Monte Carlo simulator which takes into account the most relevant Galactic inputs. Results. We find that oxygen-neon white dwarfs cannot account for a substantial fraction of the microlensing depth towards the LMC, independently of the adopted initial mass function, although some microlensing events could be due to oxygen-neon white dwarfs. Conclusions. The white dwarf population contributes at most a 5% to the mass of the Galactic halo.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

White dwarfs with hydrogen-deficient atmospheres and the dark matter content of the Galaxy

The nature of the several microlensing events observed by the MACHO team towards the Large Magellanic Cloud (LMC) is still a subject of debate. Low-mass substellar objects and stars with masses larger than ~M_{sun} have been ruled out as major components of a Massive Astrophysical Compact Halo Object (MACHO) Galactic halo, while stars of half a solar mass seem to be viable candidates. Main sequence stars have been already discarded, and there are tight restrictions on the role played by white dwarfs with hydrogen-dominated atmospheres. In this paper we evaluate the contribution to the dark matter content of the Galaxy of white dwarfs with hydrogen-deficient atmospheres. For this purpose we use a Monte Carlo simulator which incorporates up-to-date evolutionary sequences of white dwarfs with hydrogen-rich and hydrogen-deficient atmospheres. We also take into account detailed descriptions of the thick disk and the halo of our Galaxy as well as of a reliable model of the LMC. We find that the contribution of white dwarfs with hydrogen-deficient atmospheres moderately increases the theoretical estimate of the optical depth with respect to the value obtained when only hydrogen-rich white dwarfs are considered. We also find that the contribuiton of the thick disk population of white dwarfs is comparable to the halo contribution. However, the contributions of both the halo and the thick disk white-dwarf populations are still insufficient to explain the number of events observed by the MACHO team. Finally, we find that the contribution to the halo dark matter of the entire population under study is less than 10% at the 95% conficence level.Comment: 12 pages, 5 figures, accepted for publication in A&