8,172 research outputs found

    Self-similar transmission properties of aperiodic Cantor potentials in gapped graphene

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    We investigate the transmission properties of quasiperiodic or aperiodic structures based on graphene arranged according to the Cantor sequence. In particular, we have found self-similar behaviour in the transmission spectra, and most importantly, we have calculated the scalability of the spectra. To do this, we implement and propose scaling rules for each one of the fundamental parameters: generation number, height of the barriers and length of the system. With this in mind we have been able to reproduce the reference transmission spectrum, applying the appropriate scaling rule, by means of the scaled transmission spectrum. These scaling rules are valid for both normal and oblique incidence, and as far as we can see the basic ingredients to obtain self-similar characteristics are: relativistic Dirac electrons, a self-similar structure and the non-conservation of the pseudo-spin. This constitutes a reduction of the number of conditions needed to observe self-similarity in graphene-based structures, see D\'iaz-Guerrero et al. [D. S. D\'iaz-Guerrero, L. M. Gaggero-Sager, I. Rodr\'iguez-Vargas, and G. G. Naumis, arXiv:1503.03412v1, 2015]

    Un caso de hemangiosarcoma en un perro de 2 años

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    Se describe un caso de tumor maligno vascular Octubre 1987 (hemangioendotelioma maligno o hemangiosarcoma), en un perro pastor alemán hembra de 2 años de edad, que llegó a nuestra consulta con síntomas inespecíficos. Solamente tras la exploración radiográfica se pensó en la posibilidad de un proceso tumoral; la necropsia y el posterior examen hisropatológico nos dieron el diagnóstico definitivo.A case of a malign vascular neoplasm (malign hemangioendothelioma or hemangiosarcoma) is described in a 2-year-old fernale German Sbepberd dog which was brought in for an examination with inespecific signs. After radiographic exploration a tumoral process vias suspected. Necropsy and histopathologic examination lead to the definitive diagnosis

    KMOS LENsing Survey (KLENS) : morpho-kinematic analysis of star-forming galaxies at z∼2z \sim 2

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    We present results from the KMOS lensing survey-KLENS which is exploiting gravitational lensing to study the kinematics of 24 star forming galaxies at 1.4<z<3.51.4<z<3.5 with a median mass of log(M⋆/M⊙)=9.6\rm log(M_\star/M_\odot)=9.6 and median star formation rate (SFR) of 7.5 M⊙ yr−1\rm 7.5\,M_\odot\,yr^{-1}. We find that 25% of these low-mass/low-SFR galaxies are rotation dominated, while the majority of our sample shows no velocity gradient. When combining our data with other surveys, we find that the fraction of rotation dominated galaxies increases with the stellar mass, and decreases for galaxies with a positive offset from the main sequence. We also investigate the evolution of the intrinsic velocity dispersion, σ0\sigma_0, as a function of the redshift, zz, and stellar mass, M⋆\rm M_\star, assuming galaxies in quasi-equilibrium (Toomre Q parameter equal to 1). From the z−σ0z-\sigma_0 relation, we find that the redshift evolution of the velocity dispersion is mostly expected for massive galaxies (log(M⋆/M⊙)>10\rm log(M_\star/M_\odot)>10). We derive a M⋆−σ0\rm M_\star-\sigma_0 relation, using the Tully-Fisher relation, which highlights that a different evolution of the velocity dispersion is expected depending on the stellar mass, with lower velocity dispersions for lower masses, and an increase for higher masses, stronger at higher redshift. The observed velocity dispersions from this work and from comparison samples spanning 0<z<3.50<z<3.5 appear to follow this relation, except at higher redshift (z>2z>2), where we observe higher velocity dispersions for low masses (log(M⋆/M⊙)∼9.6\rm log(M_\star/M_\odot)\sim 9.6) and lower velocity dispersions for high masses (log(M⋆/M⊙)∼10.9\rm log(M_\star/M_\odot)\sim 10.9) than expected. This discrepancy could, for instance, suggest that galaxies at high-zz do not satisfy the stability criterion, or that the adopted parametrisation of the specific star formation rate and molecular properties fail at high redshift.Comment: Accepted for publication in A&A, 21 pages, 10 figure

    An extremely high velocity molecular jet surrounded by an ionized cavity in the protostellar source Serpens SMM1

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    We report ALMA observations of a one-sided, high-velocity (∼\sim80 km s−1^{-1}) CO(J=2→1J = 2 \rightarrow 1) jet powered by the intermediate-mass protostellar source Serpens SMM1-a. The highly collimated molecular jet is flanked at the base by a wide-angle cavity; the walls of the cavity can be seen in both 4 cm free-free emission detected by the VLA and 1.3 mm thermal dust emission detected by ALMA. This is the first time that ionization of an outflow cavity has been directly detected via free-free emission in a very young, embedded Class 0 protostellar source that is still powering a molecular jet. The cavity walls are ionized either by UV photons escaping from the accreting protostellar source, or by the precessing molecular jet impacting the walls. These observations suggest that ionized outflow cavities may be common in Class 0 protostellar sources, shedding further light on the radiation, outflow, and jet environments in the youngest, most embedded forming stars.Comment: 6 pages, 4 figures, accepted for publication in the Astrophysical Journal Letter

    Interaction Effects on the Magneto-optical Response of Magnetoplasmonic Dimers

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    The effect that dipole-dipole interactions have on the magneto-optical (MO) properties of magnetoplasmonic dimers is theoretically studied. The specific plasmonic versus magnetoplasmonic nature of the dimer's metallic components and their specific location within the dimer plays a crucial role on the determination of these properties. We find that it is possible to generate an induced MO activity in a purely plasmonic component, even larger than that of the MO one, therefore dominating the overall MO spectral dependence of the system. Adequate stacking of these components may allow obtaining, for specific spectral regions, larger MO activities in systems with reduced amount of MO metal and therefore with lower optical losses. Theoretical results are contrasted and confirmed with experiments for selected structures

    Uncertainty quantification and predictability of wind speed over the Iberian Peninsula

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    During recent decades, the use of probabilistic forecasting methods has increased markedly. However, these predictions still need improvement in uncertainty quantification and predictability analysis. For this reason, the main aim of this paper is to develop tools for quantifying uncertainty and predictability of wind speed over the Iberian Peninsula. To achieve this goal, several spread indexes extracted from an ensemble prediction system are defined in this paper. Subsequently, these indexes were evaluated with the aim of selecting the most appropriate for the characterization of uncertainty associated to the forecasting. Selection is based on comparison of the average magnitude of ensemble spread (ES) and mean absolute percentage error (MAPE). MAPE is estimated by comparing the ensemble mean with wind speed values from different databases. Later, correlation between MAPE and ES was evaluated. Furthermore, probability distribution functions (PDFs) of spread indexes are analyzed to select the index with greater similarity to MAPE PDFs. Then, the spread index selected as optimal is used to carry out a spatiotemporal analysis of model uncertainty in wind forecasting. The results indicate that mountainous regions and the Mediterranean coast are characterized by strong uncertainty, and the spread increases more rapidly in areas affected by strong winds. Finally, a predictability index is proposed for obtaining a tool capable of providing information on whether the predictability is higher or lower than average. The applications developed may be useful in the forecasting of wind potential several days in advance, with substantial importance for estimating wind energy production

    Weak and Compact Radio Emission in Early High-Mass Star Forming Regions: I. VLA Observations

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    We present a high sensitivity radio continuum survey at 6 and 1.3 \,cm using the Karl G. Jansky Very Large Array towards a sample of 58 high-mass star forming regions. Our sample was chosen from dust clumps within infrared dark clouds with and without IR sources (CMC-IRs, CMCs, respectively), and hot molecular cores (HMCs), with no previous, or relatively weak radio continuum detection at the 1 1\,mJy level. Due to the improvement in the continuum sensitivity of the VLA, this survey achieved map rms levels of ∼\sim 3-10 μ\muJy beam−1^{-1} at sub-arcsecond angular resolution. We extracted 70 centimeter continuum sources associated with 1.2 \,mm dust clumps. Most sources are weak, compact, and are prime candidates for high-mass protostars. Detection rates of radio sources associated with the mm dust clumps for CMCs, CMC-IRs and HMCs are 6%\%, 53%\% and 100%\%, respectively. This result is consistent with increasing high-mass star formation activity from CMCs to HMCs. The radio sources located within HMCs and CMC-IRs occur close to the dust clump centers with a median offset from it of 12,000 \,AU and 4,000 \,AU, respectively. We calculated 5 - 25 \,GHz spectral indices using power law fits and obtain a median value of 0.5 (i.e., flux increasing with frequency), suggestive of thermal emission from ionized jets. In this paper we describe the sample, observations, and detections. The analysis and discussion will be presented in Paper II.Comment: Accepted for publication in the ApJ

    Fiber sensors for the high-speed railway environment

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    Specialty Optical Fibers 2014, Barcelona, Spain, 27–31 July 2014We review some recent work on fiber-optic sensors for the high-speed railway environment. In particular, we show convenient fiber-optic solutions for rail and wheel monitoring, perimeter security and catenary protection in changeover section
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