Dabo: pliegos de poesía

Abstract not availabl

Características de la anidación de la tortuga verde Chelonia mydas (Testudinata, Cheloniidae) en la playa Caleta de los Piojos, Cuba, a partir de marcaciones externas

Green turtle (Chelonia mydas) females nesting during 2002 and 2003 nesting seasons at Caleta de los Piojos Beach, Cuba, were studied using data from individual tagging. Nesting occurred on average twice per season with a mean interval of 10.9 days. A high number of turtles nested only once per season (39% and 40% respectively). The percentage of failed multiple nesting attempts was high in both seasons. However, the percentage of failed attempts prior to the first nesting was higher in the 2003 season. Vegetation areas seem to be the most suitable sites for nesting and have a significant effect on nest–site selection behaviour. Fidelity to first nest–site was high, 50.3% and 72.9% respectively for 2002 and 2003. Observed mean clutch size (117 eggs) was closely related to body dimensions. Key words: Green turtle, Chelonia mydas, Nesting, Tagging, Guanahacabibes Peninsula.En el presente estudio se caracterizan aspectos reproductivos de las hembras de tortuga verde (Chelonia mydas), que anidaron entre los años 2002 y 2003, en la playa Caleta de los Piojos, Cuba. Se utiliza la información recopilada a partir de la colocación de marcas metálicas en cada tortuga observada. Durante las temporadas en estudio se comprobó que las tortugas anidan dos veces como promedio, con intervalo de 10.9 días. Un gran número de tortugas anidaron sólo una vez en toda la etapa reproductiva (39% y 40% respectivamente). El mayor porcentaje de intentos fallidos de anidación para ambos años ocurrió entre anidaciones consecutivas. Sin embargo en la temporada de anidación 2003 se observó un mayor porcentaje de intentos fallidos antes de la primera anidación, respecto al año 2002. La zona de vegetación fue la más utilizada para la anidación y tiene un efecto significativo en la conducta de selección del sitio de anidación. Se observó un 50,3% y 72,9% respectivamente para 2002 y 2003, de fidelidad al lugar de primera anidación. El tamaño promedio de la nidada (117 huevos) depende de las dimensiones corporales de la hembra anidadora. Palabras clave: Tortuga verde, Chelonia mydas, Anidación, Marcación, Península de Guanahacabibes

Dry anaerobic digestion of organic waste: A review of operational parameters and their impact on process performance.

open access articleDry digestion is a suitable technology for treating organic wastes with varying composition such as the organic fraction of municipal solids waste. Yet, there is a need for further research to overcome some of the disadvantages associated with the high total solids content of the process. Optimisation of inoculum to substrate ratio, feedstock composition and size, liquid recirculation, bed compaction and use of bulking agents are some of the parameters that need further investigation in batch dry anaerobic digestion, to limit localised inhibition effects and avoid process instability. In addition, further attention on the relation between feedstock composition, organic loading rate and mixing regimes is required for continuous dry anaerobic digestion systems. This paper highlights all the areas where knowledge is scarce and value can be added to increase dry anaerobic digestion performance and expansion

Spin depolarization in the transport of holes across GaMnAs/GaAlAs/p-GaAs

We study the spin polarization of tunneling holes injected from ferromagnetic GaMnAs into a p-doped semiconductor through a tunneling barrier. We obtain an upper limit to the spin injection rate. We find that spin-orbit interaction interaction in the barrier and in the drain limits severely spin injection. Spin depolarization is stronger when the magnetization is parallel to the current than when is perpendicular to it.Comment: Accepted in Phys. Rev. B. 4 pages, 4 figure

On Evidence-based Risk Management in Requirements Engineering

Background: The sensitivity of Requirements Engineering (RE) to the context makes it difficult to efficiently control problems therein, thus, hampering an effective risk management devoted to allow for early corrective or even preventive measures. Problem: There is still little empirical knowledge about context-specific RE phenomena which would be necessary for an effective context- sensitive risk management in RE. Goal: We propose and validate an evidence-based approach to assess risks in RE using cross-company data about problems, causes and effects. Research Method: We use survey data from 228 companies and build a probabilistic network that supports the forecast of context-specific RE phenomena. We implement this approach using spreadsheets to support a light-weight risk assessment. Results: Our results from an initial validation in 6 companies strengthen our confidence that the approach increases the awareness for individual risk factors in RE, and the feedback further allows for disseminating our approach into practice.Comment: 20 pages, submitted to 10th Software Quality Days conference, 201

Poisson approximations for the Ising model

A $d$-dimensional Ising model on a lattice torus is considered. As the size $n$ of the lattice tends to infinity, a Poisson approximation is given for the distribution of the number of copies in the lattice of any given local configuration, provided the magnetic field $a=a(n)$ tends to $-\infty$ and the pair potential $b$ remains fixed. Using the Stein-Chen method, a bound is given for the total variation error in the ferromagnetic case.Comment: 25 pages, 1 figur

Forward-backward equations for nonlinear propagation in axially-invariant optical systems

We present a novel general framework to deal with forward and backward components of the electromagnetic field in axially-invariant nonlinear optical systems, which include those having any type of linear or nonlinear transverse inhomogeneities. With a minimum amount of approximations, we obtain a system of two first-order equations for forward and backward components explicitly showing the nonlinear couplings among them. The modal approach used allows for an effective reduction of the dimensionality of the original problem from 3+1 (three spatial dimensions plus one time dimension) to 1+1 (one spatial dimension plus one frequency dimension). The new equations can be written in a spinor Dirac-like form, out of which conserved quantities can be calculated in an elegant manner. Finally, these new equations inherently incorporate spatio-temporal couplings, so that they can be easily particularized to deal with purely temporal or purely spatial effects. Nonlinear forward pulse propagation and non-paraxial evolution of spatial structures are analyzed as examples.Comment: 11 page