A Nexafs Study of Nitric Oxide Layers Adsorbed from a nitrite Solution onto a Pt(111) Surface

NO molecules adsorbed on a Pt(111) surface from dipping in an acidic nitrite solution are studied by near edge X-ray absorption fine structure spectroscopy (NEXAFS), X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and scanning tunnelling microscopy (STM) techniques. LEED patterns and STM images show that no long range ordered structures are formed after NO adsorption on a Pt(111) surface. Although the total NO coverage is very low, spectroscopic features in N K-edge and O K-edge absorption spectra have been singled out and related to the different species induced by this preparation method. From these measurements it is concluded that the NO molecule is adsorbed trough the N atom in an upright conformation. The maximum saturation coverage is about 0.3 monolayers, and although nitric oxide is the major component, nitrite and nitrogen species are slightly co-adsorbed on the surface. The results obtained from this study are compared with those previously reported in the literature for NO adsorbed on Pt(111) under UHV conditions

The Top Ten solar analogs in the ELODIE library

Several solar analogs have been identified in the library of high resolution stellar spectra taken with the echelle spectrograph ELODIE. A purely differential method has been used, based on the chi2 comparison of a large number of G dwarf spectra to 8 spectra of the Sun, taken on the Moon and Ceres. HD 146233 keeps its status of closest ever solar twin (Porto de Mello & da Silva 1997). Some other spectroscopic analogs have never been studied before, while the two planet-host stars HD095128 and HD186427 are also part of the selection. The fundamental parameters found in the literature for these stars show a surprising dispersion, partly due to the uncertainties which affect them. We discuss the advantages and drawbacks of photometric and spectroscopic methods to search for solar analogs and conclude that they have to be used jointly to find real solar twins.Comment: 12 pages, accepted in A&

Near-Infrared Polarimetric Adaptive Optics Observations of NGC 1068: A torus created by a hydromagnetic outflow wind

We present J' and K' imaging linear polarimetric adaptive optics observations of NGC 1068 using MMT-Pol on the 6.5-m MMT. These observations allow us to study the torus from a magnetohydrodynamical (MHD) framework. In a 0.5" (30 pc) aperture at K', we find that polarisation arising from the passage of radiation from the inner edge of the torus through magnetically aligned dust grains in the clumps is the dominant polarisation mechanism, with an intrinsic polarisation of 7.0%$\pm$2.2%. This result yields a torus magnetic field strength in the range of 4$-$82 mG through paramagnetic alignment, and 139$^{+11}_{-20}$ mG through the Chandrasekhar-Fermi method. The measured position angle (P.A.) of polarisation at K$'$ is found to be similar to the P.A. of the obscuring dusty component at few parsec scales using infrared interferometric techniques. We show that the constant component of the magnetic field is responsible for the alignment of the dust grains, and aligned with the torus axis onto the plane of the sky. Adopting this magnetic field configuration and the physical conditions of the clumps in the MHD outflow wind model, we estimate a mass outflow rate $\le$0.17 M$_{\odot}$ yr$^{-1}$ at 0.4 pc from the central engine for those clumps showing near-infrared dichroism. The models used were able to create the torus in a timescale of $\geq$10$^{5}$ yr with a rotational velocity of $\leq$1228 km s$^{-1}$ at 0.4 pc. We conclude that the evolution, morphology and kinematics of the torus in NGC 1068 can be explained within a MHD framework.Comment: 14 pages, 4 figures, Accepted by MNRA

Stimulus - response curves of a neuronal model for noisy subthreshold oscillations and related spike generation

We investigate the stimulus-dependent tuning properties of a noisy ionic conductance model for intrinsic subthreshold oscillations in membrane potential and associated spike generation. On depolarization by an applied current, the model exhibits subthreshold oscillatory activity with occasional spike generation when oscillations reach the spike threshold. We consider how the amount of applied current, the noise intensity, variation of maximum conductance values and scaling to different temperature ranges alter the responses of the model with respect to voltage traces, interspike intervals and their statistics and the mean spike frequency curves. We demonstrate that subthreshold oscillatory neurons in the presence of noise can sensitively and also selectively be tuned by stimulus-dependent variation of model parameters.Comment: 19 pages, 7 figure

Sub-arcsec mid-IR observations of NGC 1614: Nuclear star-formation or an intrinsically X-ray weak AGN?

We present new mid-infrared N-band spectroscopy and Q-band photometry of the local luminous infrared galaxy NGC1614, one of the most extreme nearby starbursts. We analyze the mid-IR properties of the nucleus (central 150 pc) and four regions of the bright circumnuclear (diameter~600 pc) star-forming (SF) ring of this object. The nucleus differs from the circumnuclear SF ring by having a strong 8-12 micron continuum (low 11.3 micron PAH equivalent width). These characteristics, together with the nuclear X-ray and sub-mm properties, can be explained by an X-ray weak active galactic nucleus (AGN), or by peculiar SF with a short molecular gas depletion time and producing an enhanced radiation field density. In either case, the nuclear luminosity (L(IR) < 6e43 erg/s) is only <5% of the total bolometric luminosity of NGC1614. So this possible AGN does not dominate the energy output in this object. We also compare three star-formation rate (SFR) tracers (Pa$\alpha$, 11.3 micron PAH, and 24 micron emissions) at 150 pc scales in the circumnuclear ring. In general, we find that the SFR is underestimated (overestimated) by a factor of 2-4 (2-3) using the 11.3 micron PAH (24 micron) emission with respect to the extinction corrected Pa$\alpha$ SFR. The former can be explained because we do not include diffuse PAH emission in our measurements, while the latter might indicate that the dust temperature is particularly warmer in the central regions of NGC1614.Comment: Accepted for publication in MNRAS; 10 pages, 5 figure

AEGIS: New Evidence Linking Active Galactic Nuclei to the Quenching of Star Formation

Utilizing Chandra X-ray observations in the All-wavelength Extended Groth Strip International Survey (AEGIS) we identify 241 X-ray selected Active Galactic Nuclei (AGNs, L > 10^{42} ergs/s) and study the properties of their host galaxies in the range 0.4 < z < 1.4. By making use of infrared photometry from Palomar Observatory and BRI imaging from the Canada-France-Hawaii Telescope, we estimate AGN host galaxy stellar masses and show that both stellar mass and photometric redshift estimates (where necessary) are robust to the possible contamination from AGNs in our X-ray selected sample. Accounting for the photometric and X-ray sensitivity limits of the survey, we construct the stellar mass function of X-ray selected AGN host galaxies and find that their abundance decreases by a factor of ~2 since z~1, but remains roughly flat as a function of stellar mass. We compare the abundance of AGN hosts to the rate of star formation quenching observed in the total galaxy population. If the timescale for X-ray detectable AGN activity is roughly 0.5-1 Gyr--as suggested by black hole demographics and recent simulations--then we deduce that the inferred AGN "trigger" rate matches the star formation quenching rate, suggesting a link between these phenomena. However, given the large range of nuclear accretion rates we infer for the most massive and red hosts, X-ray selected AGNs may not be directly responsible for quenching star formation.Comment: 12 pages. Submitted to ApJ. Comments welcom

ALMA resolves the torus of NGC 1068: continuum and molecular line emission

We have used the Atacama Large Millimeter Array (ALMA) to map the emission of the CO(6-5) molecular line and the 432 {\mu}m continuum emission from the 300 pc-sized circumnuclear disk (CND) of the nearby Seyfert 2 galaxy NGC 1068 with a spatial resolution of ~4 pc. These observations spatially resolve the CND and, for the first time, image the dust emission, the molecular gas distribution, and the kinematics from a 7-10 pc-diameter disk that represents the submillimeter counterpart of the putative torus of NGC 1068. We fitted the nuclear spectral energy distribution of the torus using ALMA and near and mid-infrared (NIR/MIR) data with CLUMPY models. The mass and radius of the best-fit solution for the torus are both consistent with the values derived from the ALMA data alone: Mgas_torus=(1+-0.3)x10^5 Msun and Rtorus=3.5+-0.5 pc. The dynamics of the molecular gas in the torus show non-circular motions and enhanced turbulence superposed on the rotating pattern of the disk. The kinematic major axis of the CO torus is tilted relative to its morphological major axis. By contrast with the nearly edge-on orientation of the H2O megamaser disk, we have found evidence suggesting that the molecular torus is less inclined (i=34deg-66deg) at larger radii. The lopsided morphology and complex kinematics of the torus could be the signature of the Papaloizou-Pringle instability, long predicted to likely drive the dynamical evolution of active galactic nuclei (AGN) tori.Comment: Final version accepted by the Astrophysical Journal Letters (ApJLetters) on April 27th 2016, 6 pages, 5 figure

Renormalization Group Analysis of a Quivering String Model of Posture Control

Scaling concepts and renormalization group (RG) methods are applied to a simple linear model of human posture control consisting of a trembling or quivering string subject to damping and restoring forces. The string is driven by uncorrelated white Gaussian noise intended to model the corrections of the physiological control system. We find that adding a weak quadratic nonlinearity to the posture control model opens up a rich and complicated phase space (representing the dynamics) with various non-trivial fixed points and basins of attraction. The transition from diffusive to saturated regimes of the linear model is understood as a crossover phenomenon, and the robustness of the linear model with respect to weak non-linearities is confirmed. Correlations in posture fluctuations are obtained in both the time and space domain. There is an attractive fixed point identified with falling. The scaling of the correlations in the front-back displacement, which can be measured in the laboratory, is predicted for both the large-separation (along the string) and long-time regimes of posture control.Comment: 20 pages, 13 figures, RevTeX, accepted for publication in PR

Efecto de la suplementación con Bacillus amyloliquefaciens y heptanoato sódico sobre los parámetros de crecimiento en conejos en cebo

El objetivo de este trabajo fue evaluar el efecto de suplementar con B. amyloliquefaciens (Ecobiol; EU aditivo zootécnico para piensos número 4b1822; contenido de 1 x 109 CFU de B. amyloliquefaciens CECT 5940 / g) y heptanoato sódico (Hepton) sobre los parámetros de crecimiento del conejo. Se formuló un pienso control (17,3% PB y 36,2% FND, sobre % MS), y otros tres piensos suplementando el pienso control con 500 y 1000 g B. amyloliquefaciens/t (BA1 y BA2) y con 1000 g heptanoato sódico/t. Se utilizaron gazapos destetados a los 25 d gazapos (67/pienso). Los conejos suplementados con el pienso BA2 tendieron a comer menos que el grupo control (P = 0,073), y comieron un 6% menos que los del grupo BA1 (P = 0,036) durante el periodo de 25 a 40 d de edad, si bien no afectó a la ganancia de peso, ni en la eficacia alimenticia. Durante el periodo de 40 a 63 d de edad los gazapos alimentados con el pienso BA2 comieron un 10% menos que el pienso control (P = 0,002), sin modificar la ganancia de peso, lo que se tradujo en una tendencia a mejorar la eficacia alimenticia (P = 0,063). Los animales del pienso BA2 incrementaron la eficacia alimenticia un 8% comparado con los del grupo BA1 durante el periodo de 40 a 63 d (P = 0,031), sin mostrar diferencias en el consumo o en la ganancia de peso. Al evaluar el periodo global, incrementar la dosis de B. amyloliquefaciens (BA2 vs. BA1) tendió a disminuir el consumo medio diario (P = 0,069) y a aumentar la eficiencia alimenticia un 6% (P = 0,006). La suplementación con B. amyloliquefaciens, independientemente de la dosis utilizada (BA2 o BA1), no afectó a la mortalidad en el periodo global del cebo. Durante todo el periodo experimental de 25 a 63 d de edad, la suplementación con heptanoato sódico redujo el consumo de pienso un 5% en comparación con el grupo control (P = 0,050) y, al no modificar la velocidad de crecimiento, aumentó la eficacia alimenticia un 7% (P = 0,003). En comparación con el promedio de los gazapos suplementados con B. amyloliquefaciens los conejos que recibieron heptanoato sódico mostraron una mayor ganancia de peso (5%, P = 0,012), y eficiencia alimenticia (4%, P = 0,024), alcanzando un peso final superior (P = 0,012)