8,300 research outputs found

    The Effect of the AGN Feedback on the Interstellar Medium of Early-Type Galaxies: 2D Hydrodynamical Simulations of the Low-Rotation Case

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    We present 2D hydrodynamical simulations for the evolution of early-type galaxies containing central massive black holes (MBHs), starting at age 2 Gyr. The code contains accurate and physically consistent radiative and mechanical AGN wind feedback, with parsec-scale central resolution. Mass input comes from stellar evolution; energy input includes Type Ia and II supernova and stellar heating; star-formation is included. Realistic, axisymmetric dynamical models for the galaxies are built solving the Jeans' equations. The lowest mass models (Mstar = 8 10^{10}Msun) develop global outflows sustained by SNIa's heating, ending with a significantly lower amount of hot gas and new stars. In more massive models, nuclear outbursts last to the present epoch, with large and frequent fluctuations in nuclear emission and from the gas (Lx). Each burst last ~ 10^{7.5} yr, during which (for r < 2-3 kpc) cold, inflowing, and hot, outflowing gas phases coexist. The Lx-T relation for the gas matches that of local galaxies. AGN activity causes positive feedback for star formation. Roughly half of the total mass loss is recycled into new stars (DeltaMstar), just ~ 3% of it is accreted on the MBH, the remainder being ejected from the galaxy. The ratio between the mass of gas expelled to that in to new stars, the load factor, is ~0.6. Rounder galaxies shapes lead to larger final MBH masses, DeltaMstar, and Lx. Almost all the time is spent at very low nuclear luminosities, yet one quarter of the total energy is emitted at an Eddington ratio > 0.1. The duty-cycle of AGN activity approximates 4% (Abridged).Comment: 26 pages, 15 figure, submitted to ApJ. Comments welcom

    Rain estimation from satellites: An examination of the Griffith-Woodley technique

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    The Griffith-Woodley Technique (GWT) is an approach to estimating precipitation using infrared observations of clouds from geosynchronous satellites. It is examined in three ways: an analysis of the terms in the GWT equations; a case study of infrared imagery portraying convective development over Florida; and the comparison of a simplified equation set and resultant rain map to results using the GWT. The objective is to determine the dominant factors in the calculation of GWT rain estimates. Analysis of a single day's convection over Florida produced a number of significant insights into various terms in the GWT rainfall equations. Due to the definition of clouds by a threshold isotherm the majority of clouds on this day did not go through an idealized life cycle before losing their identity through merger, splitting, etc. As a result, 85% of the clouds had a defined life of 0.5 or 1 h. For these clouds the terms in the GWT which are dependent on cloud life history become essentially constant. The empirically derived ratio of radar echo area to cloud area is given a singular value (0.02) for 43% of the sample, while the rainrate term is 20.7 mmh-1 for 61% of the sample. For 55% of the sampled clouds the temperature weighting term is identically 1.0. Cloud area itself is highly correlated (r=0.88) with GWT computed rain volume. An important, discriminating parameter in the GWT is the temperature defining the coldest 10% cloud area. The analysis further shows that the two dominant parameters in rainfall estimation are the existence of cold cloud and the duration of cloud over a point

    Cut-free Calculi and Relational Semantics for Temporal STIT Logics

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    We present cut-free labelled sequent calculi for a central formalism in logics of agency: STIT logics with temporal operators. These include sequent systems for Ldm , Tstit and Xstit. All calculi presented possess essential structural properties such as contraction- and cut-admissibility. The labelled calculi G3Ldm and G3Tstit are shown sound and complete relative to irreflexive temporal frames. Additionally, we extend current results by showing that also Xstit can be characterized through relational frames, omitting the use of BT+AC frames

    Effect of Al doping on the optical phonon spectrum in Mg(1-x)Al(x)B(2)

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    Raman and infrared absorption spectra of Mg(1-x)Al(x)B(2) have been collected for 0<x<0.5 in the spectral range of optical phonons. The x-dependence of the peak frequency, the width and the intensity of the observed Raman lines has been carefully analized. A peculiar x-dependence of the optical modes is pointed out for two different Al doping ranges. In particular the onset of the high-doping structural phase previously observed in diffraction measurements is marked by the appearence of new spectral components at high frequencies. A connection between the whole of our results and the observed suppression of superconductivity in the high doping region is established

    Biometric characterization of the Red-legged Partridges Alectoris rufa of northwestern Italy

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    The biometrics of the Red-legged Partridge Alectoris rufa has been relatively well studied in the western part of its distribution range (Iberian Peninsula and France), especially due to the available large hunting bag samples. Conversely, the Italian population is poorly characterized. We analysed a sample of 254 live birds trapped and ringed in the northern Apennines (province of Alessandria, northwestern Italy), by measuring body mass and the length of wing, eighth primary, tail, tarsus and bill. We found significant differences in some biometric measurements between sex and age classes. A subsample of birds (n = 112) was genetically tested for introgressive hybridization with A. chukar, an introduced species, showing that 16.1 % of free-living partridge are hybrid individuals. When we analysed separately "pure"and "introgressed"birds we found only small biometric differences in body mass of adult males. Finally, our results were compared with the biometry of other populations from the whole natural range of the species (France, Spain and Portugal) showing a negative biometric trend of wing length from westernmost to southeastern birds of the range. Introgressed birds found in the studied population were not easily distinguishable with biometric criteria from pure A. rufa rufa, so genetic analysis is highly recommended when planning reintroductions or restocking

    On The Low-Frequency Vibrational Modes of C60_{60}

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    The vibrational spectrum of C60_{60} is compared to the spectrum of a classical isotropic elastic spherical shell. We show correlations between the low frequency modes of C60_{60} and those of the spherical shell. We find the spherical model gives the approximate frequency ordering for the low frequency modes. We estimate a Poisson ratio of σ0.30\sigma\approx 0.30 and a transverse speed of sound of vs1800v_s\approx 1800 m/s for the equivalent elastic shell. We also find that ω(M1)/ω(M0)=32\omega({\rm M_1})/\omega({\rm M_0})=\sqrt{3\over 2} for the shell modes M0{\rm M_0} and M1{\rm M_1}, independent of elastic constants. We find that this ratio compares favorably with an experimental value of 1.17.Comment: 11 pages, 3 figures in Postscript, uses REVTEX, to be published in Chem. Phys. Let

    IDSC Hecla Response to CDAT Appeal

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    Hecla Limited\u27s Consolidated Response to the Coeur d\u27Alene Tribe\u27s Appea

    IDSC Hecla Response to USA Appeal

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    Hecla Limited\u27s Consolidated Response to the United States\u27 Appea

    IDSC Hecla Response to USA Appeal

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    Hecla Limited\u27s Consolidated Response to the United States\u27 Appea

    IDSC Hecla Response to CDAT Appeal

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    Hecla Limited\u27s Consolidated Response to the Coeur d\u27Alene Tribe\u27s Appea
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