Constraining a possible time-variation of the gravitational constant through "gravitochemical heating" of neutron stars

A hypothetical time-variation of the gravitational constant $G$ would make neutron stars expand or contract, so the matter in their interiors would depart from beta equilibrium. This induces non-equilibrium weak reactions, which release energy that is invested partly in neutrino emission and partly in internal heating. Eventually, the star arrives at a stationary state in which the temperature remains nearly constant, as the forcing through the change of $G$ is balanced by the ongoing reactions. Using the surface temperature of the nearest millisecond pulsar (PSR J0437$-$4715) inferred from ultraviolet observations and results from theoretical modelling of the thermal evolution, we estimate two upper limits for this variation: (1) $|\dot G/G| < 2 \times 10^{-10}\mathrm{yr}^{-1},$ if the fast, "direct Urca" reactions are allowed, and (2) $|\dot G/G|<4\times 10^{-12}\mathrm{yr}^{-1},$ considering only the slower, "modified Urca" reactions. The latter is among the most restrictive upper limits obtained by other methods.Comment: IAU 2009 JD9 conference proceedings. MmSAIt, vol.80, in press. Paolo Molaro & Elisabeth Vangioni, eds. - 4 pages, 2 figure

Proyectos y motivaciones ocupacionales de adolescentes que cursan el último año de la escuela secundaria

Esta investigación pretende describir y comparar los proyectos y motivaciones ocupacionales en una muestra de adolescentes que cursan el último año de la escuela secundaria, pertenecientes a niveles socio económicos diferenciados. El estudio se realizó desde un enfoque cuantitativo, y su alcance es descriptivo y comparativo. Los instrumentos utilizados fueron: una encuesta socio demográfica, el Cuestionario de Motivaciones Ocupacionales (Migone de Faletty y Moreno, 2015c) y entrevista semiestructurada. La muestra es dirigida, no probabilística, conformada por 77 participantes, de los cuales 37 pertenecen al nivel socio económico bajo y 40 al nivel socio económico medio. En los resultados, se encontró que la mayoría de los adolescentes de la muestra tiene como proyecto estudiar, aunque es mayor el porcentaje que piensa combinar estudio y trabajo como proyecto en el nivel socio económico bajo. Los participantes le otorgan mayor importancia a la motivación de satisfacción laboral para elegir su carrera u ocupación, excepto los varones del nivel socio económico bajo, que priorizan la dimensión de futuro. Finalmente, se propone realizar intervenciones de orientación vocacional en la escuela secundaria desde un enfoque preventivo, que tiendan a la equidad y a restituir las oportunidades de inserción ocupacional en los sectores más desfavorecidos.This research aims to describe and compare occupational projects and motivations in a sample of adolescents who attend the last year of secondary school, belonging to different socioeconomic levels. The study was conducted from a quantitative approach, and its scope is descriptive and comparative. The instruments used were: a sociodemographic survey, the Questionnaire of Occupational Motivations (Migone de Faletty y Moreno, 2015c) and semi-structured interview. The sample is non-probabilistic, of directed type, consisting of 77 participants, of whom 37 belong to the low socioeconomic level and 40 to the average socioeconomic level. In the results, it was found that the majority of the adolescents in the sample have study as a project, although the percentage that thinks to combine study and work as a project in the low socioeconomic level is higher. The participants give greater importance to the motivation of Job Satisfaction to choose their career or occupation, except the men of the low socioeconomic level, who prioritize the Future dimension. Finally, it is proposed to carry out vocational guidance interventions in the secondary school from a preventive approach, which tend to equity and to restore opportunities for occupational insertion in the most disadvantaged sectors.Fil: Jofré, Paula Mariel

Constraining a possible time-variation of the gravitational constant through "gravitochemical heating" of neutron stars

A hypothetical time-variation of the gravitational constant $G$ would cause neutron star matter to depart from beta equilibrium, due to the changing hydrostatic equilibrium. This forces non-equilibrium beta processes to occur, which release energy that is invested partly in neutrino emission and partly in heating the stellar interior. Eventually, the star arrives at a stationary state in which the temperature remains nearly constant, as the forcing through the change of $G$ is balanced by the ongoing reactions. Comparing the surface temperature of the nearest millisecond pulsar, PSR J0437-4715, inferred from ultraviolet observations, with our predicted stationary temperature, we estimate two upper limits for this variation: (1) $|\dot G/G| < 2 \times 10^{-10}$ yr$^{-1}$, if we allow direct Urca reactions operating in the neutron star core, and (2) $|\dot G/G| < 4 \times 10^{-12}$ yr$^{-1}$, considering only modified Urca reactions. Both results are competitive with those obtained by other methods, with (2) being among the most restrictive.Comment: 4 pages, including 2 figures. Accepted for publication in Phys. Rev. Lett. Revised version includes minor changes in the wording, and more substantial changes in the last 2 paragraphs (Discussion and Conclusions). Equations, figures, and results are unchange

J01020100-7122208::an accreted evolved blue straggler that wasn't ejected from a supermassive black hole

J01020100-7122208 is a star whose origin and nature still challenges us. It was first believed to be a yellow super giant ejected from the Small Magellanic Cloud, but it was more recently claimed to be a red giant accelerated by the Milky Way's central black hole. In order to unveil its nature, we analysed photometric, astrometric and high resolution spectroscopic observations to estimate the orbit, age, and 16 elemental abundances. Our results show that this star has a retrograde and highly-eccentric orbit, $e=0.914_{-0.020}^{+0.016}$. Correspondingly, it likely crossed the Galactic disk at $550\;\mathrm{pc}$ from the Galactic centre. We obtained a spectroscopic mass and age of $1.09\pm0.10$ $M_\odot$ and $4.51\pm1.44$ Gyr respectively. Its chemical composition is similar to the abundance of other retrograde halo stars. We found that the star is enriched in europium, having [Eu/Fe] = 0.93 $\pm$ 0.24, and is more metal-poor than reported in the literature, with [Fe/H] = -1.30 $\pm$ 0.10. This information was used to conclude that J01020100-7122208 is likely not a star ejected from the central black of the Milky Way or from the Small Magellanic Cloud. Instead, we propose that it is simply a halo star which was likely accreted by the Milky Way in the distant past but its mass and age suggest it is probably an evolved blue straggler.Comment: 17 pages, 9 Figures, accepted for publication in Monthly Notices of the Royal Astronomical Societ

Desigualdades en el ejercicio del cuidado a través del enfoque de género

Este artículo surge con el propósito de reflexionar sobre las diferencias de género presentes en la sociedad, las cuales permean al cuidado. Para ello, se describe el cuidado a lo largo de la historia, luego se desarrolla en forma extensa la temática de sistemas de cuidados, subdividida en cuidados informales y cuidados formales. Se realiza un análisis de las desigualdades de género presentes en ambos sistemas y las implicaciones de ellas para las mujeres y enfermería. Se exponen algunas propuestas para romper con los estereotipos imperantes, incorporar al hombre al cuidado informal y que Enfermería modifique su visión paradigmática. Se concluye que existe desigualdad de género en el sistema de cuidado informal y formal, que es la mujer quien asume el rol de cuidar producto de los estereotipos sociales. Este aspecto afecta a Enfermería porque parte de las desigualdades existentes en su quehacer, derivan de la visión cultural o social hacia el cuidado

Comparative analysis of atmospheric parameters from high-resolution spectroscopic sky surveys: APOGEE, GALAH, Gaia-ESO

SDSS-IV APOGEE-2, GALAH and Gaia-ESO are high resolution, ground-based, multi-object spectroscopic surveys providing fundamental stellar atmospheric parameters and multiple elemental abundance ratios for hundreds of thousands of stars of the Milky Way. We undertake a comparison between the most recent data releases of these surveys to investigate the accuracy and precision of derived parameters by placing the abundances on an absolute scale. We discuss the correlations in parameter and abundance differences as a function of main parameters. Uncovering the variants provides a basis to on-going efforts of future sky surveys. Quality samples from the APOGEE-GALAH, APOGEE-GES and GALAH-GES overlapping catalogs are collected. We investigate the mean variants between the surveys, and linear trends are also investigated. We compare the slope of correlations and mean differences with the reported uncertainties. The average and scatter of vrad, Teff, log g, [M/H] and vmicro, along with numerous species of elemental abundances in the combined catalogs show that in general there is a good agreement between the surveys. We find large radial velocity scatters ranging from 1.3 km/s to 4.4 km/s when comparing the three surveys. We observe weak trends: e.g. in $\Delta$Teff vs. $\Delta$log g for the APOGEE-GES stars, and a clear correlation in the vmicro-$\Delta$vmicro planes in the APOGEE-GALAH common sample. For [$\alpha$/H], [Ti/H] (APOGEE-GALAH giants) and [Al/H] (APOGEE-GALAH dwarfs) potential strong correlations are discovered as a function of the differences in the main atmospheric parameters, and we find weak trends for other elements. In general we find good agreement between the three surveys within their respective uncertainties. However, there are certain regimes in which strong variants exist, which we discuss. There are still offsets larger than 0.1 dex in the absolute abundance scales.Comment: Accepted in A&A, 23 pages, 13 figures, 6 tables. A minor correction is applied to the Gaia-ESO Survey's solar reference: Grevesse et al. (2007) instead of Grevesse & Sauval (1998

Discovery and Validation of a High-Density sub-Neptune from the K2 Mission

We report the discovery of BD+20594b, a high density sub-Neptune exoplanet, made using photometry from Campaign 4 of the two-wheeled Kepler (K2) mission, ground-based radial velocity follow-up from HARPS and high resolution lucky and adaptive optics imaging obtained using AstraLux and MagAO, respectively. The host star is a bright ($V=11.04$, $K_s = 9.37$), slightly metal poor ([Fe/H]$=-0.15\pm 0.05$ dex) solar analogue located at $152.1^{+9.7}_{-7.4}$ pc from Earth, for which we find a radius of $R_*=0.928^{+0.055}_{-0.040}R_\odot$ and a mass of $M_* = 0.961^{+0.032}_{-0.029}M_\odot$. A joint analysis of the K2 photometry and HARPS radial velocities reveal that the planet is in a $\approx 42$ day orbit around its host star, has a radius of $2.23^{+0.14}_{-0.11}R_\oplus$, and a mass of $16.3^{+6.0}_{-6.1}M_\oplus$. Although the data at hand puts the planet in the region of the mass-radius diagram where we could expect planets with a pure rock (i.e. magnesium silicate) composition using two-layer models (i.e., between rock/iron and rock/ice compositions), we discuss more realistic three-layer composition models which can explain the high density of the discovered exoplanet. The fact that the planet lies in the boundary between "possibly rocky" and "non-rocky" exoplanets, makes it an interesting planet for future RV follow-up.Comment: 12 pages, 11 figures. Accepted for publication in Ap

Characterization of a phage-like pyocin from the plant growth-promoting rhizobacterium Pseudomonas fluorescens SF4c

R-type and F-type pyocins are high-molecular-mass bacteriocins produced by Pseudomonas aeruginosa that resemble bacteriophage tails. They contain no head structures and no DNA, and are used as defence systems. In this report, we show that Pseudomonas fluorescens SF4c, a strain isolated from the wheat rhizosphere, produces a high-molecular-mass bacteriocin which inhibits the growth of closely related bacteria. A mutant deficient in production of this antimicrobial compound was obtained by transposon mutagenesis. Sequence analysis revealed that the transposon had disrupted a gene that we have named ptm, since it is homologous to that encoding phage tape-measure protein in P. fluorescens Pf0-1, a gene belonging to a prophage similar to phage-like pyocin from P. aeruginosa PAO1. In addition, we have identified genes from the SF4c pyocin cluster that encode a lytic system and regulatory genes. We constructed a nonpolar ptm mutant of P. fluorescens SF4c. Heterologous complementation of this mutation restored the production of bacteriocin. Real-time PCR was used to analyse the expression of pyocin under different stress conditions. Bacteriocin was upregulated by mitomycin C, UV light and hydrogen peroxide, and was downregulated by saline stress. This report constitutes, to our knowledge, the first genetic characterization of a phage tail-like bacteriocin in a rhizosphere Pseudomonas strain. © 2012 Society for General Microbiology.Fil: Fischer, Sonia Elizabeth. Consejo Superior de Investigaciones Científicas. Estación Experimental del Zaidín; España. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Investigaciones Agrobiotecnológicas. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Agrobiotecnológicas; ArgentinaFil: Godino, Agustina. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Quesada, José Miguel. Consejo Superior de Investigaciones Científicas. Estación Experimental del Zaidín; EspañaFil: Cordero Gabrielli, Paula Verónica. Universidad Nacional de Río Cuarto; Argentina. Universidad Nacional de Río Cuarto. Instituto para el Desarrollo Agroindustrial y de la Salud. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto para el Desarrollo Agroindustrial y de la Salud; ArgentinaFil: Jofré, Edgardo. Universidad Nacional de Río Cuarto. Instituto para el Desarrollo Agroindustrial y de la Salud. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto para el Desarrollo Agroindustrial y de la Salud; Argentina. Universidad Nacional de Río Cuarto; ArgentinaFil: Mori, Gladys Beatriz. Universidad Nacional de Río Cuarto; ArgentinaFil: Espinosa Urgel, Manuel. Consejo Superior de Investigaciones Científicas. Estación Experimental del Zaidín; Españ