14,884 research outputs found

    Stellar indices and kinematics in Seyfert 1 nuclei

    Get PDF
    We present spectra of 6 type 1 Seyfert galaxies, 2 Seyfert 2, a starburst galaxy and a compact narrow line radiogalaxy, taken in two spectral ranges centered around the near--IR CaII triplet (CaT) (at ~8600 Angstroms), and the Mgb stellar feature at 5180 Angstroms. We measured the equivalent width (EWs) of these features and the Fe52 and Fe53 spectral indices. We found that the strength of the CaT in type 1 Seyfert galaxies with prominent central point sources, is larger than what would be expected from the observed strength of the blue indices. This could be explained by the presence of red supergiants in the nuclei of Seyfert 1 galaxies. On the other hand, the blue indices of these galaxies could also be diluted by the strong FeII multiplets that can be seen in their spectra. We have also measured the stellar and gas velocity dispersions of the galaxies in the sample. The stellar velocity dispersions were measured using both, the Mgb and CaT stellar features. The velocity dispersion of the gas in the narrow line region (NLR) was measured using the strong emission lines [OIII] 5007, 4959 and [SIII] 9069. We compare the gas and star velocity dispersions and find that both magnitudes are correlated in Seyfert galaxies. Most of the Seyfert 1 we observe have stellar velocity dispersion somehow greater than that of the gas in the NLR.Comment: To appear in MNRAS, 18 pages, 9 figure

    Dataset concerning the analytical approximation of the Ae3 temperature.

    Get PDF
    In this paper we present a new polynomial function for calculating the local phase transformation temperature (Ae3 ) between the austenite+ferrite and the fully austenitic phase fields during heating and cooling of steel:[Formula: see text] The dataset includes the terms of the function and the values for the polynomial coefficients for major alloying elements in steel. A short description of the approximation method used to derive and validate the coefficients has also been included. For discussion and application of this model, please refer to the full length article entitled "The role of aluminium in chemical and phase segregation in a TRIP-assisted dual phase steel" 10.1016/j.actamat.2016.05.046 (Ennis et al., 2016) [1]

    Spark Plug Simulation with the Use of Three Types of Fuels in Direct Injection Engines for the Evaluation of Polluting Factors

    Get PDF
    The present work has as main objective the use of a biofuel (Ecopaís) in a direct injection vehicle, it is an option to reduce damage to health and the environment, for this a static thermal simulation will be done in the spark plug, to compare the results of the aforementioned software using On Board tests, in a 1500 cc engine. The measurements of the emission factors of CO, HC and NOx gases will be considered in a route established in the city of Quito from 2399 to 2870 meters above sea level. The interaction of the element is carried out in the ANSYS Academic program which is 14977 nodes and 7523 elements to be studied with automatic meshing, obtaining that the Ecopaís and Ecopaís + Ferox fuels have the highest heat flow with a 5% divergence compared to the Extra fuel + Ferox. There is a significant reduction in pollutant emissions of 3% of CO with the use of Ecopaís in comparison to Extra + Ferox fuel, in the case of HC, Ecopaís and Ecopaís + Ferox fuels with 3% lower emissions compared to Extra fuel + Ferox, and in NOx, fuels that have Extra + Ferox and Ecopaís + Ferox solid additives are 3 and 3.5% lower compared to Ecopaís fuel, respectively. Keywords: biofuel, termal, on board, ferox, emission factors. Resumen El presente trabajo tiene como objetivo fundamental la utilización de un biocombustible (Ecopaís) en un vehículo de inyección directa, es una opción para disminuir daños a la salud y al medio ambiente, para ello se hará una simulación térmica estática en la bujía de encendido, para comparar los resultados del mencionado software mediante pruebas On Board, en un motor de 1500 cc. Las mediciones de los factores de emisión de gases de CO, HC y NOx, se contemplará en una ruta establecida en la ciudad de Quito de 2399 hasta 2870 m.s.n.m. La interacción del elemento se realiza en el programa ANSYS Academic que es de 14977 nodos y 7523 elementos a estudiar con el mallado automático, obteniendo que los combustibles Ecopaís y Ecopaís+Ferox tienen el mayor flujo de calor con una divergencia del 5% en comparación del combustible Extra + Ferox. Se evidencia una reducción significativa de emisiones contaminantes del 2.5% del CO con el uso del Ecopaís en comparación del combustible Extra + Ferox, en el caso de HC los combustibles Ecopaís y Ecopaís + Ferox con un 1% menor en emisiones en comparación al combustible Extra + Ferox, y en el NOx los combustibles que tienen aditivo sólido Extra+Ferox y Ecopaís+Ferox son menores en un 6 y 4% con respecto al combustible Ecopaís respectivamente. Palabras clave: biocombustible, térmica, on board, ferox, factores de emisiones

    Semiempirical Modeling of Reset Transitions in Unipolar Resistive-Switching based Memristors

    Get PDF
    We have measured the transition process from the high to low resistivity states, i.e., the reset process of resistive switching based memristors based on Ni/HfO2/Si-n+ structures, and have also developed an analytical model for their electrical characteristics. When the characteristic curves are plotted in the current-voltage (I-V) domain a high variability is observed. In spite of that, when the same curves are plotted in the charge-flux domain (Q-phi), they can be described by a simple model containing only three parameters: the charge (Qrst) and the flux (rst) at the reset point, and an exponent, n, relating the charge and the flux before the reset transition. The three parameters can be easily extracted from the Q-phi plots. There is a strong correlation between these three parameters, the origin of which is still under study

    Position-dependent shear-induced austenite-martensite transformation in double-notched TRIP and dual-phase steel samples

    Get PDF
    While earlier studies on transformation-induced-plasticity (TRIP) steels focused on the determination of the austenite-to-martensite decomposition in uniform deformation or thermal fields, the current research focuses on the determination of the local retained austenite-to-martensite transformation behaviour in an inhomogeneous yet carefully controlled shear-loaded region of double-notched TRIP and dual-phase (DP) steel samples. A detailed powder analysis has been performed to simultaneously monitor the evolution of the phase fraction and the changes in average carbon concentration of metastable austenite together with the local strain components in the constituent phases as a function of the macroscopic stress and location with respect to the shear band. The metastable retained austenite shows a mechanically induced martensitic transformation in the localized shear zone, which is accompanied by an increase in average carbon concentration of the remaining austenite due to a preferred transformation of the austenite grains with the lowest carbon concentration. At the later deformation stages the geometry of the shear test samples results in the development of an additional tensile component. The experimental strain field within the probed sample area is in good agreement with finite element calculations. The strain development observed in the low-alloyed TRIP steel with metastable austenite is compared with that of steels with the same chemical composition containing either no austenite (a DP grade) or stable retained austenite (a TRIP grade produced at a long bainitic holding time). The transformation of metastable austenite under shear is a complex interplay between the local microstructure and the evolving strain fields

    Probing the Circumnuclear Stellar Populations of Starburst Galaxies in the Near-infrared

    Full text link
    We employ the NASA Infrared Telescope Facility's near-infrared spectrograph SpeX at 0.8-2.4μ\mum to investigate the spatial distribution of the stellar populations (SPs) in four well known Starburst galaxies: NGC34, NGC1614, NGC3310 and NGC7714. We use the STARLIGHT code updated with the synthetic simple stellar populations models computed by Maraston (2005, M05). Our main results are that the NIR light in the nuclear surroundings of the galaxies is dominated by young/intermediate age SPs (t2×109t \leq 2\times10^9yr), summing from \sim40\% up to 100\% of the light contribution. In the nuclear aperture of two sources (NGC1614 and NGC3310) we detected a predominant old SP component (t>2×109t > 2\times10^9yr), while for NGC34 and NGC7714 the younger component prevails. Furthermore, we found evidence of a circumnuclear star formation ring-like structure and a secondary nucleus in NGC1614, in agreement with previous studies. We also suggest that the merger/interaction experienced by three of the galaxies studied, NGC1614, NGC3310 and NGC7714 can explain the lower metallicity values derived for the young SP component of these sources. In this scenario the fresh unprocessed metal poorer gas from the destroyed/interacting companion galaxy is driven to the centre of the galaxies and mixed with the central region gas, before star formation takes place. In order to deepen our analysis, we performed the same procedure of SP synthesis using Maraston (2011, M11) EPS models. Our results show that the newer and higher resolution M11 models tend to enhance the old/intermediate age SP contribution over the younger ages

    Rigidity analysis of HIV-1 protease

    Full text link
    We present a rigidity analysis on a large number of X-ray crystal structures of the enzyme HIV-1 protease using the 'pebble game' algorithm of the software FIRST. We find that although the rigidity profile remains similar across a comprehensive set of high resolution structures, the profile changes significantly in the presence of an inhibitor. Our study shows that the action of the inhibitors is to restrict the flexibility of the beta-hairpin flaps which allow access to the active site. The results are discussed in the context of full molecular dynamics simulations as well as data from NMR experiments.Comment: 4 pages, 3 figures. Conference proceedings for CMMP conference 2010 which was held at the University of Warwic
    corecore