799 research outputs found

    Studying cetacean behaviour: new technological approaches and conservation applications

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    Animal behaviour can provide valuable information for wildlife management and conservation. Studying the detailed behaviour of marine mammals involves challenges not faced by most animal behaviour researchers due to the size, mobility and lack of continuous visibility of these animals. We describe several methods developed by marine mammal scientists to study behaviour, primarily of cetaceans, focusing on technological advances: unmanned aerial systems (UAS), satellite-linked telemetry, passive acoustics and multisensor high-resolution acoustic recording tags. We then go on to explain how the data collected by these methods have contributed to and informed conservation actions. We focus on examples including: satellite data informing the interactions between cetaceans and offshore oil and gas development; passive acoustics used to track distributions of several species of cetaceans, including their movements near shipping lanes; and high-resolution acoustic recording tags used to document responses of cetaceans to anthropogenic activities. Finally, we discuss recent efforts to link animal behaviour to individual fitness and, particularly for behavioural disturbances, to population-level consequences, which can be helpful for informing conservation efforts. The infusion of technological advancements into studies of cetacean behaviour combined with emerging analytical techniques brings us to the next 20+ years of studying these animals. These developments will improve our capabilities in areas such as testing whether their behaviour adheres to traditional behavioural theory, and will certainly assist the guiding of conservation efforts

    Stability of the lattice formed in first-order phase transitions to matter containing strangeness in protoneutron stars

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    Well into the deleptonization phase of a core collapse supernova, a first-order phase transition to matter with macroscopic strangeness content is assumed to occur and lead to a structured lattice defined by negatively charged strange droplets. The lattice is shown to crystallize for expected droplet charges and separations at temperatures typically obtained during the protoneutronstar evolution. The melting curve of the lattice for small spherical droplets is presented. The one-component plasma model proves to be an adequate description for the lattice in its solid phase with deformation modes freezing out around the melting temperature. The mechanical stability against shear stresses is such that velocities predicted for convective phenomena and differential rotation during the Kelvin-Helmholtz cooling phase might prevent the crystallization of the phase transition lattice. A solid lattice might be fractured by transient convection, which could result in anisotropic neutrino transport. The melting curve of the lattice is relevant for the mechanical evolution of the protoneutronstar and therefore should be included in future hydrodynamics simulations.Comment: accepted for publication in Physical Review

    Non-topological solitons as nucleation sites for cosmological phase transitions

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    I consider quantum field theories that admit charged non-topological solitons of the Q-ball type, and use the fact that in a first-order cosmological phase transition, below the critical temperature, there is a value of the soliton charge above which the soliton becomes unstable and expands, converting space to the true vacuum, much like a critical bubble in the case of ordinary tunneling. Using a simple model for the production rate of Q-balls through charge accretion during a random walk out of equilibrium, I calculate the probability for the formation of critical charge solitons and estimate the amount of supercooling needed for the phase transition to be completed.Comment: 20 pages, 2 figures, some comments and references adde

    Long-lived oscillons from asymmetric bubbles

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    The possibility that extremely long-lived, time-dependent, and localized field configurations (``oscillons'') arise during the collapse of asymmetrical bubbles in 2+1 dimensional phi^4 models is investigated. It is found that oscillons can develop from a large spectrum of elliptically deformed bubbles. Moreover, we provide numerical evidence that such oscillons are: a) circularly symmetric; and b) linearly stable against small arbitrary radial and angular perturbations. The latter is based on a dynamical approach designed to investigate the stability of nonintegrable time-dependent configurations that is capable of probing slowly-growing instabilities not seen through the usual ``spectral'' method.Comment: RevTeX 4, 9 pages, 11 figures. Revised version with a new approach to stability. Accepted to Phys. Rev.

    Allen Telescope Array Multi-Frequency Observations of the Sun

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    We present the first observations of the Sun with the Allen Telescope Array (ATA). We used up to six frequencies, from 1.43 to 6 GHz, and baselines from 6 to 300 m. To our knowledge, these are the first simultaneous multifrequency full-Sun maps obtained at microwave frequencies without mosaicing. The observations took place when the Sun was relatively quiet, although at least one active region was present each time. We present multi-frequency flux budgets for each sources on the Sun. Outside of active regions, assuming optically thin bremsstrahlung (free--free) coronal emission on top of an optically thick ~10 000 K chromosphere, the multi-frequency information can be condensed into a single, frequency-independent, "coronal bremsstrahlung contribution function" [EM/sqrt(T)] map. This technique allows the separation of the physics of emission as well as a measurement of the density structure of the corona. Deviations from this simple relationship usually indicate the presence of an additional gyroresonance-emission component, as is typical in active regions.Comment: 16 pages, 11 figures. Accepted for publication in Solar Physic

    The future of sovereignty in multilevel governance Europe: a constructivist reading

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    Multilevel governance presents a depiction of contemporary structures in EU Europe as consisting of overlapping authorities and competing competencies. By focusing on emerging non-anarchical structures in the international system, hence moving beyond the conventional hierarchy/anarchy dichotomy to distinguish domestic and international arenas, this seems a radical transformation of the familiar Westphalian system and to undermine state sovereignty. Paradoxically, however, the principle of sovereignty proves to be resilient despite its alleged empirical decline. This article argues that social constructivism can explain the paradox, by considering sovereign statehood as a process-dependent institutional fact, and by showing that multilevel governance can feed into this process

    Cosmic String in the Supersymmetric CSKR Theory

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    We study a cosmic string solution of an N=1-supersymmetric version of the Cremmer-Scherk-Kalb-Ramond (CSKR) Lagrangian coupled to a vector superfield by means of a topological mass term. The 2-form gauge potential is proposed to couple non-minimally to matter, here described by a chiral scalar superfield. The important outcome is that supersymmetry is kept exact both in the core and in the exterior region of the string. We contemplate the bosonic configurations and it can be checked that the solutions saturate the Bogomolnyi bound. A glimpse on the fermionic zero modes is also given.Comment: 14 pages, LaTeX, presented at the XXI "Encontro Nacional de Fisica de Particulas e Campos", Sao Lourenco, MG, Brazil, with zero modes adde

    Asteroseismology of Eclipsing Binary Stars in the Kepler Era

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    Eclipsing binary stars have long served as benchmark systems to measure fundamental stellar properties. In the past few decades, asteroseismology - the study of stellar pulsations - has emerged as a new powerful tool to study the structure and evolution of stars across the HR diagram. Pulsating stars in eclipsing binary systems are particularly valuable since fundamental properties (such as radii and masses) can determined using two independent techniques. Furthermore, independently measured properties from binary orbits can be used to improve asteroseismic modeling for pulsating stars in which mode identifications are not straightforward. This contribution provides a review of asteroseismic detections in eclipsing binary stars, with a focus on space-based missions such as CoRoT and Kepler, and empirical tests of asteroseismic scaling relations for stochastic ("solar-like") oscillations.Comment: 28 pages, 12 figures, 2 tables; Proceedings of the AAS topical conference "Giants of Eclipse" (AASTCS-3), July 28 - August 2 2013, Monterey, C

    Negative Kaons in Dense Baryonic Matter

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    Kaon polarization operator in dense baryonic matter of arbitrary isotopic composition is calculated including s- and p-wave kaon-baryon interactions. The regular part of the polarization operator is extracted from the realistic kaon-nucleon interaction based on the chiral and 1/N_c expansion. Contributions of the Lambda(1116), Sigma(1195), Sigma*(1385) resonances are taken explicitly into account in the pole and regular terms with inclusion of mean-field potentials. The baryon-baryon correlations are incorporated and fluctuation contributions are estimated. Results are applied for K- in neutron star matter. Within our model a second-order phase transition to the s-wave K- condensate state occurs at rho_c \gsim 4 \rho_0 once the baryon-baryon correlations are included. We show that the second-order phase transition to the p-wave K−K^- condensate state may occur at densities ρc∌3Ă·5ρ0\rho_c \sim 3\div 5 \rho_0 in dependence on the parameter choice. We demonstrate that a first-order phase transition to a proton-enriched (approximately isospin-symmetric) nucleon matter with a p-wave K- condensate can occur at smaller densities, \rho\lsim 2 \rho_0. The transition is accompanied by the suppression of hyperon concentrations.Comment: 41 pages, 24 figures, revtex4 styl
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