Instituto Politécnico Nacional

About: Instituto Politécnico Nacional is a education organization based out in Mexico City, Mexico. It is known for research contribution in the topics: Population & Context (language use). The organization has 43351 authors who have published 63315 publications receiving 938532 citations. The organization is also known as: Instituto Politécnico Nacional & Instituto Politecnico Nacional.

Gaia FGK benchmark stars: Metallicity

Abstract: Context. To calibrate automatic pipelines that determine atmospheric parameters of stars, one needs a sample of stars, or “benchmark stars”, with well-defined parameters to be used as a reference.Aims. We provide detailed documentation of the iron abundance determination of the 34 FGK-type benchmark stars that are selected to be the pillars for calibration of the one billion Gaia stars. They cover a wide range of temperatures, surface gravities, and metallicities.Methods. Up to seven different methods were used to analyze an observed spectral library of high resolutions and high signal-to-noise ratios. The metallicity was determined by assuming a value of effective temperature and surface gravity obtained from fundamental relations; that is, these parameters were known a priori and independently from the spectra.Results. We present a set of metallicity values obtained in a homogeneous way for our sample of benchmark stars. In addition to this value, we provide detailed documentation of the associated uncertainties. Finally, we report a value of the metallicity of the cool giant ψ Phe for the first time.

Physics potential of a long-baseline neutrino oscillation experiment using a J-PARC neutrino beam and Hyper-Kamiokande

Abstract: Hyper-Kamiokande will be a next generation underground water Cherenkov detector with a total (fiducial) mass of 0.99 (0.56) million metric tons, approximately 20 (25) times larger than that of Super-Kamiokande. One of the main goals of Hyper-Kamiokande is the study of $CP$ asymmetry in the lepton sector using accelerator neutrino and anti-neutrino beams. In this paper, the physics potential of a long baseline neutrino experiment using the Hyper-Kamiokande detector and a neutrino beam from the J-PARC proton synchrotron is presented. The analysis uses the framework and systematic uncertainties derived from the ongoing T2K experiment. With a total exposure of 7.5 MW $\times$ 10$^7$ sec integrated proton beam power (corresponding to $1.56\times10^{22}$ protons on target with a 30 GeV proton beam) to a $2.5$-degree off-axis neutrino beam, it is expected that the leptonic $CP$ phase $\delta_{CP}$ can be determined to better than 19 degrees for all possible values of $\delta_{CP}$, and $CP$ violation can be established with a statistical significance of more than $3\,\sigma$ ($5\,\sigma$) for $76\%$ ($58\%$) of the $\delta_{CP}$ parameter space. Using both $ u_e$ appearance and $ u_\mu$ disappearance data, the expected 1$\sigma$ uncertainty of $\sin^2\theta_{23}$ is 0.015(0.006) for $\sin^2\theta_{23}=0.5(0.45)$.

Side by Side: Learning by Observing and Pitching In

Abstract: This article examines cultural practices that support informal learning as children observe and pitch in with everyday activities that are integrated into family and community life. We discuss the social and cultural grounding of this learning tradition, drawing on research carried out in different parts of the world during more than 60 years. Children learn by watching, listening, and attending, often with great concentration, by taking purposeful initiative, and by contributing and collaborating. We try to correct the frequent misconception that this way of learning is essentially a nonverbal process by showing that speech is commonly used, but judiciously, in support of efficient communication rather than for “lessons.” This learning tradition is not in opposition to school learning; children with schooling experience learn this way when they belong and experience community. [informal learning, cultural practices, socialization, observation, family and community learning]

The multi-phase winds of Markarian 231: from the hot, nuclear, ultra-fast wind to the galaxy-scale, molecular outflow

Abstract: Mrk 231 is a nearby ultra-luminous IR galaxy exhibiting a kpc-scale, multi-phase AGN-driven outflow. This galaxy represents the best target to investigate in detail the morphology and energetics of powerful outflows, as well as their still poorly-understood expansion mechanism and impact on the host galaxy. In this work, we present the best sensitivity and angular resolution maps of the molecular disk and outflow of Mrk 231, as traced by CO(2−1) and (3−2) observations obtained with the IRAM/PdBI. In addition, we analyze archival deep Chandra and NuSTAR X-ray observations. We use this unprecedented combination of multi-wavelength data sets to constrain the physical properties of both the molecular disk and outflow, the presence of a highly-ionized ultra-fast nuclear wind, and their connection. The molecular CO(2−1) outflow has a size of ~1 kpc, and extends in all directions around the nucleus, being more prominent along the south-west to north-east direction, suggesting a wide-angle biconical geometry. The maximum projected velocity of the outflow is nearly constant out to ~1 kpc, thus implying that the density of the outflowing material must decrease from the nucleus outwards as ~r-2. This suggests that either a large part of the gas leaves the flow during its expansion or that the bulk of the outflow has not yet reached out to ~1 kpc, thus implying a limit on its age of ~1 Myr. Mapping the mass and energy rates of the molecular outflow yields OF = [500−1000] M⊙ yr-1 and Ėkin,OF = [7−10] × 10^(43) erg s^(-1). The total kinetic energy of the outflow is Ekin,OF is of the same order of the total energy of the molecular disk, Edisk. Remarkably, our analysis of the X-ray data reveals a nuclear ultra-fast outflow (UFO) with velocity −20 000 km s^(-1), UFO = [0.3−2.1] M_⊙ yr^(-1), and momentum load UFO/ rad = [0.2−1.6]. We find Ėkin,UFO ~ Ėkin,OF as predicted for outflows undergoing an energy conserving expansion. This suggests that most of the UFO kinetic energy is transferred to mechanical energy of the kpc-scale outflow, strongly supporting that the energy released during accretion of matter onto super-massive black holes is the ultimate driver of giant massive outflows. The momentum flux OF derived for the large scale outflows in Mrk 231 enables us to estimate a momentum boost OF/ UFO ≈ [30−60]. The ratios Ėkin,UFO/Lbol,AGN = [1−5] % and Ėkin,OF/Lbol,AGN = [1−3] % agree with the requirements of the most popular models of AGN feedback.

Preparation, characterization and photocatalytic activity of ZnO, Fe2O3 and ZnFe2O4

Abstract: ZnO, Fe 2 O 3 and ZnFe 2 O 4 were synthesized by precipitation or coprecipitation at constant pH After aging, washing and drying, the solids were calcined at 800 C The samples were characterized by XRD, TGA, N 2 physisorption, UV-Vis and TPR The photocatalytic degradation of phenol was studied in a batch reactor and TiO 2 (Degussa, P-25) was used as a reference catalyst Pure ZnO and Fe 2 O 3 were obtained at 800 C, whereas ZnFe 2 O 4 and α-Fe 2 O 3 (segregated) were detected in the zinc ferrite sample TPR experiments showed the reduction peaks in the range of 350-800 C only with Fe 2 O 3 and ZnFe 2 O 4 , attributed to Fe 3+ to Fe 2+ reduction and complete dehydroxylation The photodegradation of phenol (samples calcined at 800 C) showed small but significant variations that decreased in the order: TiO 2 > ZnFe 2 O 4 > ZnO > Fe 2 O 3 Subproducts such as hydroquinone, catechol and benzoquinone were mainly detected In particular, attention was focused on our prepared materials because after 24 h they did not dissolve as happened with TiO 2