Estructura espacial y de talla de una población de la gorgonia Paramuricea macrospina (Anthozoa, Alcyonacea) en la plataforma continental del canal de Menorca.

Trabajo final presentado por Stefano Ambroso para el Master en Ciencias del Mar: Oceanografía y Gestión del Medio Marino de la Universitat de Barcelona (UB), realizado bajo la dirección del Dr. Josep Maria Gili Sardà y del Dr. Andrea Gori del Institut de Ciències del Mar (ICM-CSIC).-- 28 pages, 11 figures, 3 tablesLa información que existe de las gorgonias mediterráneas que habitan las plataformas continentales, en comparación con la que se tiene de las poblaciones someras, es muy escasa. Esto se debe a la profundidad que limita su accesibilidad y por lo tanto su estudio. En el mar Mediterráneo noroccidental se encontraron altas densidades de la gorgonia Paramuricea macrospina (Koch, 1882) a profundidades entre 85 y 90 m sobre todo en fondos de maërl. Sobre la ecología de esta especie hay poca información, por lo tanto, nuestros objetivos se enfocaron en investigar su estructura de talla y de población. En septiembre de 2010 y abril de 2011 en el Canal de Menorca se grabaron 10 vídeo-transectos con un sumergible tripulado (JAGO). Mediante el análisis de estos transectos pudimos concluir que la clase de talla más abundante de Paramuricea macrospina es la que está entre 10 y 20 cm. Además, se encontró una distribución agrupada en toda el área examinada y patrones espaciales a pequeña y media escala. Comparando nuestros resultados con los de otros estudios sobre otras especies mediterráneas, Paramuricea macrospina presenta una altura media inferior a la de Paramuricea clavata y una distribución espacial que no llega a cubrir regularmente el sustrato como en el caso de Eunicella singularis. Esto se debe a que los fondos de maërl presentan una menor estabilidad y una mayor vulnerabilidad a los efectos de la pesca, que el sustrato rocosoPeer Reviewe

Misurare la competenza in italiano come L.2. Alcune considerazione e proposte.

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Interdistrict Choice and Teacher Beliefs: Implications for Educational Expectations, Equity, and Policymaking

Interdistrict choice, which allows families to choose between schools outside of their districts of residence, is currently serving more students than any other choice program in the United States. Yet, despite this popularity, there is a pressing need for more research on how interdistrict choice may affect educational equity within U.S. public schools. Drawing on the analytic framework of educational racial contract, this study examines the issue of teacher beliefs in the context of interdistrict choice at a large, urban high school in Arizona, where market-based school choice programs have been continually expanded for nearly three decades. Data were collected through a survey of 112 teachers, who rated their in- district and out-of-district students based on their perception of three developmental skill categories: 1) academic, 2) communication, and 3) behavior. Results speak to negative teacher beliefs about the educability of Students of Color and hold significant implications for teachers’ academic expectations, educational equity, and future policy decisions

Two Higgs Pair Heterotic Vacua and Flavor-Changing Neutral Currents

We present a vacuum of heterotic M-theory whose observable sector has the MSSM spectrum with the addition of one extra pair of Higgs-Higgs conjugate superfields. The quarks/leptons have a realistic mass hierarchy with a naturally light first family. The double elliptic structure of the Calabi-Yau compactification threefold leads to two ``stringy'' selection rules. These classically disallow Yukawa couplings to the second Higgs pair and, hence, Higgs mediated flavor-changing neutral currents. Such currents are induced in higher-dimensional interactions, but are naturally suppressed. We show that our results fit comfortably below the observed upper bounds on neutral flavor-changing processes.Comment: 52 pages, 3 figures, 1 table, requires feynm

The B-L/Electroweak Hierarchy in Heterotic String and M-Theory

E8 x E8 heterotic string and M-theory, when compactified on a Calabi-Yau threefold admitting an SU(4) vector bundle with Wilson lines, can give rise to the exact MSSM spectrum with three right-handed neutrino chiral superields, one per family. Rank preserving Wilson lines require that the standard model group be augmented by a gauged U(1)_B-L. Since there are no fields in this theory for which 3(B-L) is an even, non-zero integer, the gauged B-L symmetry must be spontaneously broken at a low scale, not too far above the electroweak scale. It is shown that in these heterotic standard models, the B-L symmetry can be broken, with a phenomenologically viable B-L/electroweak hierarchy, by at least one right-handed sneutrino acquiring a vacuum expectation value. This is explicitly demonstrated, in a specific region of parameter space, using a renormalization group analysis and soft supersymmetry breaking operators. The vacuum state is shown to be a stable, local minimum of the potential and the resultant hierarchy is explicitly presented in terms of tan[beta].Comment: 16 pages; typos fixed, analysis generalize

Dynamics of shallow impact cratering

We present data for the time-dependence of wooden spheres penetrating into a loose non-cohesive packing of glass beads. The stopping time is a factor of three longer than the time $d/v_\circ$ needed to travel the total penetration distance $d$ at the impact speed $v_\circ$. The acceleration decreases monotonically throughout the impact. These kinematics are modelled by a position- and velocity-dependent stopping force that is constrained to reproduce prior observations for the scaling of the penetration depth with the total drop distance.Comment: 4 pages, experimen

Coupling techniques for nonlinear hyperbolic equations. III. The well-balanced approximation of thick interfaces

We continue our analysis of the coupling between nonlinear hyperbolic problems across possibly resonant interfaces. In the first two parts of this series, we introduced a new framework for coupling problems which is based on the so-called thin interface model and uses an augmented formulation and an additional unknown for the interface location; this framework has the advantage of avoiding any explicit modeling of the interface structure. In the present paper, we pursue our investigation of the augmented formulation and we introduce a new coupling framework which is now based on the so-called thick interface model. For scalar nonlinear hyperbolic equations in one space variable, we observe that the Cauchy problem is well-posed. Then, our main achievement in the present paper is the design of a new well-balanced finite volume scheme which is adapted to the thick interface model, together with a proof of its convergence toward the unique entropy solution (for a broad class of nonlinear hyperbolic equations). Due to the presence of a possibly resonant interface, the standard technique based on a total variation estimate does not apply, and DiPerna's uniqueness theorem must be used. Following a method proposed by Coquel and LeFloch, our proof relies on discrete entropy inequalities for the coupling problem and an estimate of the discrete entropy dissipation in the proposed scheme.Comment: 21 page

A Godunov-type method for the seven-equation model of compressible two-phase flow

We are interested in the numerical approximation of the solutions of the compressible seven-equation two-phase flow model. We propose a numerical srategy based on the derivation of a simple, accurate and explicit approximate Riemann solver. The source terms associated with the external forces and the drag force are included in the definition of the Riemann problem, and thus receive an upwind treatment. The objective is to try to preserve, at the numerical level, the asymptotic property of the solutions of the model to behave like the solutions of a drift-flux model with an algebraic closure law when the source terms are stiff. Numerical simulations and comparisons with other strategies are proposed

A method to couple HEM and HRM two-phase flow models

International audienceWe present a method for the unsteady coupling of two distinct two-phase flow models (namely the Homogeneous Relaxation Model, and the Homogeneous Equilibrium Model) through a thin interface. The basic approach relies on recent works devoted to the inter-facial coupling of CFD models, and thus requires to introduce an interface model. Many numerical test cases enable to investigate the stability of the coupling method

Penetration depth for shallow impact cratering

We present data for the penetration of a variety of spheres, dropped from rest, into a level non-cohesive granular medium. We improve upon our earlier work [Uehara {\it et al.} Phys. Rev. Lett. {\bf 90}, 194301 (2003)] in three regards. First, we explore the behavior vs sphere diameter and density more systematically, by holding one of these parameters constant while varying the other. Second, we prepare the granular medium more reproducibly and, third, we measure the penetration depth more accurately. The new data support our previous conclusion that the penetration depth is proportional to the 1/2 power of sphere density, the 2/3 power of sphere diameter, and the 1/3 power of total drop distance