Marine Protected Areas effectively maintain endemic Pinna nobilis populations

Coastal habitat degradation compromise sessile marine species. Populations of the endemic species, fan shell bivalve Pinna nobilis are declining in spite of species protection. Models analyzed environmental versus human-derived stressors as explanatory variables depicting populations at mesoscale level. Human stressors explained most variability in density spatial distribution significantly disturbing benthic communities, while habitat protection affected P. nobilis structure and physical aggression by anchoring highly impact on densities. Environmental variables played a secondary role, indicating that global change processes are not so relevant in coastal benthic communities as human-derived impacts

Rate of Convergence to Barenblatt Profiles for the Fast Diffusion Equation

We study the asymptotic behaviour of positive solutions of the Cauchy problem for the fast diffusion equation near the extinction time. We find a continuum of rates of convergence to a self-similar profile. These rates depend explicitly on the spatial decay rates of initial data

Gravitational shocks as a key ingredient of Gamma-Ray Bursts

We identify a novel physical mechanism that may be responsible for energy release in $\gamma$-ray bursts. Radial perturbations in the neutron core, induced by its collision with collapsing outer layers during the early stages of supernova explosions, can trigger a gravitational shock, which can readily eject a small but significant fraction of the collapsing material at ultra-relativistic speeds. The development of such shocks is a strong-field effect arising in near-critical collapse in General Relativity and has been observed in numerical simulations in various contexts, including in particular radially perturbed neutron star collapse, albeit for a tiny range of initial conditions. Therefore, this effect can be easily missed in numerical simulations if the relevant parameter space is not exhaustively investigated. In the proposed picture, the observed rarity of $\gamma$-ray bursts would be explained if the relevant conditions for this mechanism appear in only about one in every $10^4-10^5$ core collapse supernovae. We also mention the possibility that near-critical collapse could play a role in powering the central engines of Active Galactic Nuclei.Comment: 9 pages, 3 figure

Porous medium equation with nonlocal pressure

We provide a rather complete description of the results obtained so far on the nonlinear diffusion equation $u_t=\nabla\cdot (u^{m-1}\nabla (-\Delta)^{-s}u)$, which describes a flow through a porous medium driven by a nonlocal pressure. We consider constant parameters $m>1$ and $0<s<1$, we assume that the solutions are non-negative, and the problem is posed in the whole space. We present a theory of existence of solutions, results on uniqueness, and relation to other models. As new results of this paper, we prove the existence of self-similar solutions in the range when $N=1$ and $m>2$, and the asymptotic behavior of solutions when $N=1$. The cases $m = 1$ and $m = 2$ were rather well known.Comment: 24 pages, 2 figure

Pattern-wavelength coarsening from topological dynamics in silicon nanofoams

We report the experimental observation of a submicron cellular structure on the surface of silicon targets eroded by an ion plasma. Analysis by atomic force microscopy allows us to assess the time evolution and show that the system can be described quantitatively by the convective Cahn-Hilliard equation, found in the study of domain coarsening for a large class of driven systems. The space-filling trait of the ensuing pattern relates it to evolving foams. Through this connection, we are actually able to derive the coarsening law for the pattern wavelength from the nontrivial topological dynamics of the cellular structure. Thus, the study of the topological properties of patterns in nonvariational spatially extended systems emerges as complementary to morphological approaches to their challenging coarsening properties.This work has been partially supported by MICINN and MEC (Spain) via Grants No. IS2009-12964-C05-01, No. FIS2009-12964-C05-03, No. FIS2012-38866-C05-01, No. IS2012-38866-C05-01-05, No. MAT2011-27470-C02-02, and No. CSD2009-00013.Publicad

Self-Organized Ordering of Nanostructures Produced by Ion-Beam Sputtering

We study the self-organized ordering of nanostructures produced by ion-beam sputtering (IBS) of targets amorphizing under irradiation. By introducing a model akin to models of pattern formation in aeolian sand dunes, we extend consistently the current continuum theory of erosion by IBS. We obtain new non-linear effects responsible for the in-plane ordering of the structures, whose strength correlates with the degree of ordering found in experiments. Our results highlight the importance of redeposition and surface viscous flow to this nanopattern formation process.Comment: 4 pages, 2 figure

Web promotion, innovation and postgraduate e-learning programs.

This study analyzes the diffusion that the main Spanish universities carry out in their corporate web pages in relation to the e-learning programs, both semi-online and online. The objective is to know if this diffusion takes into account the communication of methodological aspects and trends that could be differentiators of an innovative offer.To this end, the most prestigious Spanish universities (public and private) have been selected, as well as those relevant in the field of e-learning. Subsequently, using the methodology "Counting methods" (Law, Qi and Buhalis, 2010), (translated into Spanish as method of itemization), the websites of each of the 689 programs offered have been analyzed. The research allows identifying the common variables used in the web promotion of all universities, and contrasts the presence of the main trends in e-learning as differentiating elements of a competitive offer.

Isotopic tissue fractionation at bivalve Pinna nobilis, a non-invasive approach

Carbon and nitrogen isotopic values of muscle and mantle in Mediterranean endemic bivalve Pinna nobilis individuals have been analyzed to study tissue fractionation. Muscle tissue is enriched in both δ13C and δ15N compared to mantle on average 1.11 ‰ and 0.71 ‰, respectively. Analyses of mantle tissue do not involve sacrifice of individuals and are therefore proposed as a conservation tool in the study of P. nobilis

Applying Fourier analyses to assess influence of environmental factors on shell morphology of Mediterranean endemic bivalve Pinna nobilis

Environmental factors such as depth or hydrodynamics can influence the morphology of Pinna nobilis. In the present work the variation in shape morphology was studied by Fourier analysis according to different environmental conditions. Important differences were found within juveniles and adults. Discriminant analysis with elliptical Fourier descriptors was able to classify with high accuracy 97.1% of the individuals according to the factors studie