1,589 research outputs found
Nanoindentation and wear behavior of thermally stable biocompatible polysulfone-alumina nanocomposites
The authors would like to acknowledge funding from the Spanish Ministerio de EconomĂa y Competitividad under grant MAT2014-57557-R. R. Prof. Ozisik would like to acknowledge financial support from the U.S. National Science Foundation (CMMI-1538730). The authors also would like to thank I. Garc´ıa and A. Cervera from Euroortodoncia for their invaluable help in nanocomposite processing
The nuclear and extended mid-infrared emission of Seyfert galaxies
We present subarcsecond resolution mid-infrared (MIR) images obtained with
8-10 m-class ground-based telescopes of a complete volume-limited (DL<40 Mpc)
sample of 24 Seyfert galaxies selected from the Swift/BAT nine month catalog.
We use those MIR images to study the nuclear and circumnuclear emission of the
galaxies. Using different methods to classify the MIR morphologies on scales of
~400 pc, we find that the majority of the galaxies (75-83%) are extended or
possibly extended and 17-25% are point-like. This extended emission is compact
and it has low surface brightness compared with the nuclear emission, and it
represents, on average, ~30% of the total MIR emission of the galaxies in the
sample. We find that the galaxies whose circumnuclear MIR emission is dominated
by star formation show more extended emission (650+-700 pc) than AGN-dominated
systems (300+-100 pc). In general, the galaxies with point-like MIR
morphologies are face-on or moderately inclined (b/a~0.4-1.0), and we do not
find significant differences between the morphologies of Sy1 and Sy2. We used
the nuclear and circumnuclear fluxes to investigate their correlation with
different AGN and SF activity indicators. We find that the nuclear MIR emission
(the inner ~70 pc) is strongly correlated with the X-ray emission (the harder
the X-rays the better the correlation) and with the [O IV] lambda 25.89 micron
emission line, indicating that it is AGN-dominated. We find the same results,
although with more scatter, for the circumnuclear emission, which indicates
that the AGN dominates the MIR emission in the inner ~400 pc of the galaxies,
with some contribution from star formation.Comment: 27 pages, 12 figures, accepted by MNRA
On stability and controllability of multi-agent linear systems
Recent advances in communication and computing have made the control and coordination of dynamic network agents to become an area of multidisciplinary research at the intersection of the theory of control systems, communication and linear algebra. The advances of the research in multi-agent systems are strongly supported by their critical applications in different areas as for example in consensus problem of communication networks, or formation control of mobile robots. Mainly, the consensus problem has been studied from the point of view of stability. Nevertheless, recently some researchers have started to analyze the controllability problems. The study of controllability is motivated by the fact that the architecture of communication network in engineering multi-agent systems is usually adjustable. Therefore, it is meaningful to analyze how to improve the controllability of a multi-agent system. In this work we analyze the stability and controllability of multiagent systems consisting of k + 1 agents with dynamics xÂżi = Aixi + Biui, i = 0, 1, . . . , kPostprint (published version
Irreversibility in quantum maps with decoherence
The Bolztmann echo (BE) is a measure of irreversibility and sensitivity to
perturbations for non-isolated systems. Recently, different regimes of this
quantity were described for chaotic systems. There is a perturbative regime
where the BE decays with a rate given by the sum of a term depending on the
accuracy with which the system is time-reversed and a term depending on the
coupling between the system and the environment. In addition, a parameter
independent regime, characterised by the classical Lyapunov exponent, is
expected. In this paper we study the behaviour of the BE in hyperbolic maps
that are in contact with different environments. We analyse the emergence of
the different regimes and show that the behaviour of the decay rate of the BE
is strongly dependent on the type of environment.Comment: 13 pages, 3 figures
On the ubiquity of trivial torsion on elliptic curves
The purpose of this paper is to give a "down--to--earth" proof of the
well--known fact that a randomly chosen elliptic curve over the rationals is
most likely to have trivial torsion
The nuclear and extended infrared emission of the Seyfert galaxy NGC 2992 and the interacting system Arp 245
We present subarcsecond resolution infrared (IR) imaging and mid-IR
spectroscopic observations of the Seyfert 1.9 galaxy NGC 2992, obtained with
the Gemini North Telescope and the Gran Telescopio CANARIAS (GTC). The N-band
image reveals faint extended emission out to ~3 kpc, and the PAH features
detected in the GTC/CanariCam 7.5-13 micron spectrum indicate that the bulk of
this extended emission is dust heated by star formation. We also report
arcsecond resolution MIR and far-IR imaging of the interacting system Arp 245,
taken with the Spitzer Space Telescope and the Herschel Space Observatory.
Using these data, we obtain nuclear fluxes using different methods and find
that we can only recover the nuclear fluxes obtained from the subarcsecond data
at 20-25 micron, where the AGN emission dominates. We fitted the nuclear IR
spectral energy distribution of NGC 2992, including the GTC/CanariCam nuclear
spectrum (~50 pc), with clumpy torus models. We then used the best-fitting
torus model to decompose the Spitzer/IRS 5-30 spectrum (~630 pc) in AGN and
starburst components, using different starburst templates. We find that,
whereas at shorter mid-IR wavelengths the starburst component dominates (64% at
6 micron), the AGN component reaches 90% at 20 micron. We finally obtained dust
masses, temperatures and star formation rates for the different components of
the Arp 245 system and find similar values for NGC 2992 and NGC 2993. These
measurements are within those reported for other interacting systems in the
first stages of the interaction.Comment: 20 pages, 12 figures, accepted by MNRA
Kovacs-like memory effect in driven granular gases
While memory effects have been reported for dense enough disordered systems
such as glasses, we show here by a combination of analytical and simulation
techniques that they are also intrinsic to the dynamics of dilute granular
gases. By means of a certain driving protocol, we prepare the gas in a state
where the granular temperature coincides with its long time limit. However,
does not subsequently remain constant, but exhibits a non-monotonic
evolution before reaching its non-equilibrium steady value. The corresponding
so-called Kovacs hump displays a normal behavior for weak dissipation (as
observed in molecular systems), but is reversed under strong dissipation, where
it thus becomes anomalous.Comment: 5 pages, to appear in Physical Review Letter
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