Effects of age and culling on movements and dispersal rates of yellow-legged gulls (Larus michahellis) from a western mediterranean colony

This study reports the effects of age and culling of breeding adults on movements and dispersal rates of Yellow-legged Gulls (Larus michahellis) from a western Mediterranean colony (the Medes Islands) based on recaptures and resightings of birds banded as chicks. Juveniles (1-year-old birds) were most frequently located in the French coast of Biscay and in the Western North Mediterranean. Older gulls became concentrated near the colony and its surroundings (core area), with 3rd year sub-adults and adults accounting for more than 70% and 90% of resightings in this area, respectively. Culling of breeding adults increased the dispersal rate of juveniles (pre-cull: 62.6% ± 6.0 SD; post-cull: 71.2% ± 6.4 SD) and mean distance of resightings of juveniles (pre-cull: 250.5 km ± 267.6 SD; post-cull: 367.6 km ± 300.1 SD), and favored displacement of juveniles to the French Atlantic coast. Culling also increased the dispersal rate of adults (pre-cull: 31.7% ± 16.6 SD; post-cull: 38.8% ± 16.3 SD) and mean distance of adult resightings (pre-cull: 27.4 km ± 108.7 SD; post-cull: 35.7 km ± 113.0 SD). This could be attributed to an increase in the number of gulls recruited to other colonies near the Medes Islands after culls. Culling performed in the Medes Islands colony seems to have effects at metapopulation level, conditioning the dynamics and management of other coloniesPostprint (author's final draft

Super-Resolution for Overhead Imagery Using DenseNets and Adversarial Learning

Recent advances in Generative Adversarial Learning allow for new modalities of image super-resolution by learning low to high resolution mappings. In this paper we present our work using Generative Adversarial Networks (GANs) with applications to overhead and satellite imagery. We have experimented with several state-of-the-art architectures. We propose a GAN-based architecture using densely connected convolutional neural networks (DenseNets) to be able to super-resolve overhead imagery with a factor of up to 8x. We have also investigated resolution limits of these networks. We report results on several publicly available datasets, including SpaceNet data and IARPA Multi-View Stereo Challenge, and compare performance with other state-of-the-art architectures.Comment: 9 pages, 9 figures, WACV 2018 submissio

Safety of Lithium Nickel Cobalt Aluminum Oxide Battery Packs in Transit Bus Applications

The future of mass transportation is clearly moving toward the increased efficiency and greenhouse gas reduction of hybrid and electric vehicles. With the introduction of high-power/high-energy storage devices such as lithium ion battery systems serving as a key element in the system, valid safety and security concerns emerge. This is especially true when the attractive high-specific-energy and power-chemistry lithium nickel cobalt aluminum oxide (NCA) is used. This chemistry provides great performance but presents a safety and security risk when used in large quantities, such as for a large passenger bus. If triggered, the cell can completely fuel its own fire, and this triggering event occurs more easily than one may think. To assist engineers and technicians in this transfer from the use of primarily fossil fuels to battery energy storage on passenger buses, the Battery Application Technology Testing and Energy Research Laboratory (BATTERY) of the Thomas D. Larson Pennsylvania Transportation Institute (LTI) in the College of Engineering at The Pennsylvania State University partnered with advanced chemistry battery and material manufacturers to study the safety concerns of an NCA battery chemistry for use in transit buses. The research team ran various experiments on cells and modules, studying rarely considered thermal events or venting events. Special considerations were made to gather supporting information to help better understand what happens, and most importantly how to best mitigate these events and/or manage them when they occur on a passenger bus. The research team found that the greatest safety concern when using such a high-energy chemistry is ensuring passenger safety when a cell’s electrolyte boils and causes the ventilation of high-temperature toxic material. A cell-venting event can be triggered by a variety of scenarios with differing levels of likelihood. Also, though the duration of a venting event is relatively short, on the order of just a few seconds, the temperature of the venting material and cell is extremely high. During a venting event, the high-pressure, burning gases tend to burn holes in nearby packaging materials. Most interestingly, the team discovered that following a venting event the large-format cells tested immediately reached and remained at extremely high external skin temperatures for very long periods, on the order of hours. The majority of this report covers the testing designed to better understand how high-energy cells of this chemistry fail and what materials can be used to manage these failures in a way that increases passenger survivability

Bitcoin mining, the clean energy accelerator

The increase in the production of electricity from renewable sources, basically wind and solar, produces strong imbalances between instant production and demand. Currently we do not have systems for large-scale ematching of energy in the moments when supply exceeds demand. This can cause problems of stability in the electrical grid, and worsens the return on investment made in production facilities. This project aims to study the proposal to use surplus energy to mine Bitcoin, thus reducing the problems of overloading the electricity grid, and improving the economic return of renewable energy installations.El incremento de la producción de energía eléctrica a partir de fuentes renovables, básicamente eólica y solar, produce fuertes desajustes entre la producción y la demanda instantáneas. Actualmente no disponemos de sistemas para el almacenamiento a gran escala de energía en los momentos donde la oferta supera la demanda. Esto puede producir problemas de estabilidad en la red eléctrica, y empeora el retorno de la inversión hecha en las instalaciones de producción. En este proyecto se quiere estudiar la propuesta de utilizar los excedente de energía para minar Bitcoin, reduciendo así los problemas de sobrecarga de la red eléctrica, y mejorando el retorno económico de las instalaciones de energías renovables.L'increment del la producció d'energia elèctrica a partir de fonts renovables, bàsicamet eòlica i solar, produeix forts desajustos entre la producció i la demanda instantànies. Actualment no disposem de sistemes per a l'emagatzematge a gran escala d'energia ens els moments on la oferta supera la demanda. Això pot produeix problemes d'estabilitat els la xarxa elèctrica, i empitjora el retorn de la inversió feta en les instal.lacions de producció. En aquest projecte es vol estudiar la proposta d'utilitzar els excedent d'energia per a minar Bitcoin, reduïnt així els problemes de sobrecàrrega de la xarxa elèctrica, i millorant el retorn econòmic de les instal.lacions d'energies renovables

The radio to TeV orbital variability of the microquasar LSI+61303

Context: .The microquasar LS I +61 303 has recently been detected at TeV energies by the Cherenkov telescope MAGIC, presenting variability on timescales similar to its orbital period. This system has been intensively observed at different wavelengths during the last three decades, showing a very complex behavior along the orbit.Aims: .We aim to explain, using a leptonic model in the accretion scenario, the observed orbital variability and spectrum from radio to TeV energies of LS I +61 303.Methods: .We apply a leptonic model based on accretion of matter from the slow inhomogeneous equatorial wind of the primary star, assuming particle injection proportional to the accretion rate. The relativistic electron energy distribution within the binary system is computed taking into account convective/adiabatic and radiative losses. The spectral energy distribution (SED) has been calculated accounting for synchrotron and (Thomson/Klein Nishina -KN-) inverse Compton (IC) processes and the photon-photon absorption in the ambient photon fields. The angle dependence of the photon-photon and IC cross sections has been considered in the calculations.Results: .We reproduce the main features of the observed light curves from LS I +61 303 at radio, X-rays, high-energy (HE), and very high-energy (VHE) gamma-rays, and the whole spectral energy distribution.Conclusions: .Our model is able to explain the radio to TeV orbital variability taking into account that radiation along the orbit is strongly affected by the variable accretion rate, the magnetic field strength, and by the ambient photon field via dominant IC losses and photon-photon absorption at periastron.Fil: Bosch Ramon, Valentí. Universidad de Barcelona; EspañaFil: Paredes, Josep Maria. Universidad de Barcelona; EspañaFil: Romero, Gustavo Esteban. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; ArgentinaFil: Ribó, Marc. Universidad de Barcelona; Españ

MUSE observations of M87: radial gradients for the stellar initial-mass function and the abundance of Sodium

Based on MUSE integral-field data we present evidence for a radial variation at the low-mass end of the stellar initial-mass function (IMF) in the central regions of the giant early-type galaxy NGC4486 (M87). We used state-of-the-art stellar population models and the observed strength of various IMF-sensitive absorption-line features to solve for the best low-mass tapered "bimodal" form of the IMF, while accounting also for radial variations in stellar metallicity, the overall $\alpha$-elements abundance, and the abundance of individual elements such as Ti, O, Na and Ca. Our analysis reveals a strong IMF gradient in M87, corresponding to an exceeding fraction of low-mass stars compared to the case of the Milky Way toward the center of M87 that drops to nearly Milky-way levels by 0.4 $R_e$. This IMF gradient is found to correlate well with both the radial profile for stellar metallicity and for $\alpha$-elements abundance but not with stellar velocity dispersion. Such IMF variations correspond to over a factor two increase in stellar mass-to-light M/L ratio compared to the case of a Milky-way like IMF, consistent with other investigations into IMF gradients in early-type galaxies, including recent dynamical constraints on M/L radial variations in M87 by Oldham & Auger. In addition to constraining the IMF in M87 we also looked into the abundance of Sodium, which turned up to be super-Solar over the entire radial range of our MUSE observations and to exhibit a considerable negative gradient. These findings suggest an additional role of metallicity in boosting the Na-yields in the central, metal-rich regions of M87 during its early and brief star-formation history. Our work adds the case of M87 to the few objects that as of today have radial constraints on their IMF or [Na/Fe] abundance, while also illustrating the accuracy that MUSE could bring to this kind of investigations.Comment: 17 pages, 13 figures, re-submitted for publication on MNRAS following the referee's comment

A Stellar Dynamical Mass Measurement of the Black Hole in NGC 3998 from Keck Adaptive Optics Observations

We present a new stellar dynamical mass measurement of the black hole in the nearby, S0 galaxy NGC 3998. By combining laser guide star adaptive optics observations obtained with the OH-Suppressing Infrared Imaging Spectrograph on the Keck II telescope with long-slit spectroscopy from the Hubble Space Telescope and the Keck I telescope, we map out the stellar kinematics on both small spatial scales, well within the black hole sphere of influence, and on large scales. We find that the galaxy is rapidly rotating and exhibits a sharp central peak in the velocity dispersion. Using the kinematics and the stellar luminosity density derived from imaging observations, we construct three-integral, orbit-based, triaxial stellar dynamical models. We find the black hole has a mass of M_BH = (8.1_{-1.9}^{+2.0}) x 10^8 M_sun, with an I-band stellar mass-to-light ratio of M/L = 5.0_{-0.4}^{+0.3} M_sun/L_sun (3-sigma uncertainties), and that the intrinsic shape of the galaxy is very round, but oblate. With the work presented here, NGC 3998 is now one of a very small number of galaxies for which both stellar and gas dynamical modeling have been used to measure the mass of the black hole. The stellar dynamical mass is nearly a factor of four larger than the previous gas dynamical black hole mass measurement. Given that this cross-check has so far only been attempted on a few galaxies with mixed results, carrying out similar studies in other objects is essential for quantifying the magnitude and distribution of the cosmic scatter in the black hole mass - host galaxy relations.Comment: 19 pages, 15 figures, accepted for publication in Ap