1,741 research outputs found

    Owls (Strigiformes) in Parque Nacional Peneda-Gerês (PNPG) – Portugal

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    Owls (Strigiformes) are particularly difficult to study and the existing information is still scarce. In PNPG area there are records of the seven species present in Portugal; the Long-eared Owl and the Short-eared Owl are here occasional species. This work aims to determine the distribution, density and abundance of Strigiformes in PNPG (Northwest of Portugal). Between December 2007 and June 2008, 106 passive hearing point counts of 15 minutes each were done in the centre of each of 106 squares (2x2 km). Distribution maps for each species were obtained. Therefore, we recorded a total of 98 contacts for Tawny Owl and 67 contacts for Scops Owl. We also obtained 7 contacts of Little Owl, 2 contacts of Barn Owl and one of Eagle Owl. The habitat selection by Scops Owl and Tawny Owl was also studied. Scops Owls seems to avoid low shrub and preferred forested areas. Tawny Owls also avoid low shrub areas, preferring forested areas, and were found in urban areas. The populations of these two species in PNPG show a considerable expansion, while the other ones reveal a marked decline regarding the previous situation. The implementation of monitoring and conservation measures is suggested to stop the decline of these three species

    Gas Emissions From the Western Aleutians Volcanic Arc

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    The Aleutian Arc is remote and highly active volcanically. Its 4,000 km extent from mainland Alaska to Russia\u2019s Kamchatka peninsula hosts over 140 volcanic centers of which about 50 have erupted in historic times. We present data of volcanic gas samples and gas emission measurements obtained during an expedition to the western-most segment of the arc in September 2015 in order to extend the sparse knowledge on volatile emissions from this remote but volcanically active region. Some of the volcanoes investigated here have not been sampled for gases before this writing. Our data show that all volcanoes host high-temperature magmatic-hydrothermal systems and have gas discharges typical of volcanoes in oceanic arcs. Based on helium isotopes, the western Aleutian Arc segment has minimal volatile contributions from the overriding crust. Volcanic CO2 fluxes from this arc segment are small, compared to the emissions from volcanoes on the Alaska Peninsula and mainland Alaska. The comparatively low CO2 emissions may be related to the lower sediment flux delivered to the trench in this part of the arc

    Collective edge modes in fractional quantum Hall systems

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    Over the past few years one of us (Murthy) in collaboration with R. Shankar has developed an extended Hamiltonian formalism capable of describing the ground state and low energy excitations in the fractional quantum Hall regime. The Hamiltonian, expressed in terms of Composite Fermion operators, incorporates all the nonperturbative features of the fractional Hall regime, so that conventional many-body approximations such as Hartree-Fock and time-dependent Hartree-Fock are applicable. We apply this formalism to develop a microscopic theory of the collective edge modes in fractional quantum Hall regime. We present the results for edge mode dispersions at principal filling factors ν=1/3,1/5\nu=1/3,1/5 and ν=2/5\nu=2/5 for systems with unreconstructed edges. The primary advantage of the method is that one works in the thermodynamic limit right from the beginning, thus avoiding the finite-size effects which ultimately limit exact diagonalization studies.Comment: 12 pages, 9 figures, See cond-mat/0303359 for related result

    Invariant Measures and Decay of Correlations for a Class of Ergodic Probabilistic Cellular Automata

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    We give new sufficient ergodicity conditions for two-state probabilistic cellular automata (PCA) of any dimension and any radius. The proof of this result is based on an extended version of the duality concept. Under these assumptions, in the one dimensional case, we study some properties of the unique invariant measure and show that it is shift-mixing. Also, the decay of correlation is studied in detail. In this sense, the extended concept of duality gives exponential decay of correlation and allows to compute explicitily all the constants involved

    Variability type classification of multi-epoch surveys

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    The classification of time series from photometric large scale surveys into variability types and the description of their properties is difficult for various reasons including but not limited to the irregular sampling, the usually few available photometric bands, and the diversity of variable objects. Furthermore, it can be seen that different physical processes may sometimes produce similar behavior which may end up to be represented as same models. In this article we will also be presenting our approach for processing the data resulting from the Gaia space mission. The approach may be classified into following three broader categories: supervised classification, unsupervised classifications, and "so-called" extractor methods i.e. algorithms that are specialized for particular type of sources. The whole process of classification- from classification attribute extraction to actual classification- is done in an automated manner.Comment: 6 pages, 2 figures. Version with figures as sent to the Editor/AIP (though not as published). Minor corrections mad

    Hamiltonian Description of Composite Fermions: Magnetoexciton Dispersions

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    A microscopic Hamiltonian theory of the FQHE, developed by Shankar and myself based on the fermionic Chern-Simons approach, has recently been quite successful in calculating gaps in Fractional Quantum Hall states, and in predicting approximate scaling relations between the gaps of different fractions. I now apply this formalism towards computing magnetoexciton dispersions (including spin-flip dispersions) in the ν=1/3\nu=1/3, 2/5, and 3/7 gapped fractions, and find approximate agreement with numerical results. I also analyse the evolution of these dispersions with increasing sample thickness, modelled by a potential soft at high momenta. New results are obtained for instabilities as a function of thickness for 2/5 and 3/7, and it is shown that the spin-polarized 2/5 state, in contrast to the spin-polarized 1/3 state, cannot be described as a simple quantum ferromagnet.Comment: 18 pages, 18 encapsulated ps figure

    Star formation histories in mergers: the spatially resolved properties of the early-stage merger luminous infrared galaxies IC 1623 and NGC 6090

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    The role of major mergers in galaxy evolution is investigated through a detailed characterization of the stellar populations, ionized gas properties and star formation rates (SFR) in the early-stage merger luminous infrared galaxies (LIRGs) IC 1623 W and NGC 6090, by analysing optical integral field spectroscopy and high-resolution Hubble Space Telescope imaging. The spectra were processed with the starlight full spectral fitting code, and the emission lines measured in the residual spectra. The results are compared with non-interacting control spiral galaxies from the Calar Alto Legacy Integral Field Area survey. Merger-induced star formation is extended and recent, as revealed by the young ages (50–80 Myr) and high contributions to light of young stellar populations (50–90 per cent), in agreement with merger simulations in the literature. These early-stage mergers have positive central gradients of the stellar metallicity, with an average ∼0.6 Z⊙. Compared to non-interacting spirals, they have lower central nebular metallicity, and flatter profiles, in agreement with the gas inflow scenario. We find that they are dominated by star formation, although shock excitation cannot be discarded in some regions, where high velocity dispersion is found (170–200 km s−1). The average SFR in these early-stage mergers (∼23–32 M⊙ yr−1) is enhanced with respect to main-sequence Sbc galaxies by factors of 6–9, slightly above the predictions from classical merger simulations, but still possible in about 15 per cent of major galaxy mergers, where U/LIRGs belong

    Journalism, journalism education and a region's integration: The case of Southeast Asia

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    The 50-year-old Association of Southeast Asian Nations (ASEAN) is now in its third year implementing the mechanics of regional integration. How does this region-wide development affect journalism in individual countries and in the region? This qualitative research sought to find out the meaning and implications of regional integration to journalism practice and education in Southeast Asia. There is enthusiasm over developing a model on ‘ASEAN-centered journalism and journalism education’, however there are country-level realities that news organisations and journalism schools face before proceeding to even attuning reportage and journalism instruction to the needs of ASEAN.Jeremaiah M. Opiniano, Aira L. Bagtas, Karl C. Basco, Raplh J. Hernandez, Elyssa C. Lopez, Michael C. Rodolfo and Anne K. Vich

    Hamiltonian theory of gaps, masses and polarization in quantum Hall states: full disclosure

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    I furnish details of the hamiltonian theory of the FQHE developed with Murthy for the infrared, which I subsequently extended to all distances and apply it to Jain fractions \nu = p/(2ps + 1). The explicit operator description in terms of the CF allows one to answer quantitative and qualitative issues, some of which cannot even be posed otherwise. I compute activation gaps for several potentials, exhibit their particle hole symmetry, the profiles of charge density in states with a quasiparticles or hole, (all in closed form) and compare to results from trial wavefunctions and exact diagonalization. The Hartree-Fock approximation is used since much of the nonperturbative physics is built in at tree level. I compare the gaps to experiment and comment on the rough equality of normalized masses near half and quarter filling. I compute the critical fields at which the Hall system will jump from one quantized value of polarization to another, and the polarization and relaxation rates for half filling as a function of temperature and propose a Korringa like law. After providing some plausibility arguments, I explore the possibility of describing several magnetic phenomena in dirty systems with an effective potential, by extracting a free parameter describing the potential from one data point and then using it to predict all the others from that sample. This works to the accuracy typical of this theory (10 -20 percent). I explain why the CF behaves like free particle in some magnetic experiments when it is not, what exactly the CF is made of, what one means by its dipole moment, and how the comparison of theory to experiment must be modified to fit the peculiarities of the quantized Hall problem

    Distinct roles of SNARE-mimicking lipopeptides during initial steps of membrane fusion

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    NWOSupramolecular & Biomaterials Chemistr
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