La ciencia según futuros profesores : entre la tradición y la novedad

Este trabajo se enmarca en una investigación que tiene por objetivo diseñar y estudiar escenarios de formación de docentes de ciencia, situados en contextos institucionales diversos. La perspectiva teórica asumida recoge los enfoques actuales acerca de la formación docente y el pensamiento del profesor; complementados con una visión que reconoce el valor del discurso en la construcción, no sólo del pensamiento, sino también de las realidades en que se insertan los sujetos. En este trabajo, tomamos uno de los escenarios de FD implementado con un grupo de estudiantes de profesorado y analizamos secuencias didácticas (SD) que éstos elaboran para la enseñanza de un contenido escolar de ciencias. Lo que nos interesa conocer es cómo, a través del discurso, los estudiantes construyen modos particulares de concebir la ciencia y cómo proyectan prácticas docentes al respecto

La ciencia según futuros profesores : entre la tradición y la novedad

Este trabajo se enmarca en una investigación que tiene por objetivo diseñar y estudiar escenarios de formación de docentes de ciencia, situados en contextos institucionales diversos. La perspectiva teórica asumida recoge los enfoques actuales acerca de la formación docente y el pensamiento del profesor; complementados con una visión que reconoce el valor del discurso en la construcción, no sólo del pensamiento, sino también de las realidades en que se insertan los sujetos. En este trabajo, tomamos uno de los escenarios de FD implementado con un grupo de estudiantes de profesorado y analizamos secuencias didácticas (SD) que éstos elaboran para la enseñanza de un contenido escolar de ciencias. Lo que nos interesa conocer es cómo, a través del discurso, los estudiantes construyen modos particulares de concebir la ciencia y cómo proyectan prácticas docentes al respecto

Milk consumption after exercise decreases electrolyte excretion.

La rehidratación es fundamental para la correcta recuperación posterior al ejercicio físico y el deporte. Las bebidas lácteas parecen ser una buena opción como bebidas rehidratantes después del ejercicio, pero aún los mecanismos no están completamente dilucidados. El presente estudio tiene por objetivo medir los efectos en la excreción de electrolitos en la orina al rehidratar con una bebida láctea baja en grasa o una bebida isotónica tras la realización de una sesión de ejercicio intermitente. 14 sujetos físicamente activos (23 ± 4 años), se dividieron en dos grupos: 1) rehidratación con bebida isotónica (ISO) y 2) rehidratación con bebida láctea baja en grasa (LBG). Se evaluó la gravedad específica de la orina (GEO), electrolitos (Na+ y K+) en orina y retención de fluidos, después del ejercicio y 4 horas posterior a la rehidratación. Se encontraron diferencias significativas en la GEO y en la excreción de K+ en el grupo LBG (p<0.005), ambos grupos muestran diferencias significativas en la excreción de Na+. Los resultados muestran que la rehidratación con bebida láctea mejora la GEO y disminuyen la excreción de K+ de forma más eficiente que la bebida isotónica posterior al ejercicioRehydration is essential for post-exercise and sport recovery. Milk seems to be a good option like sport drinks after exercise, yet the rehydration mechanisms are still not fully understood. The aim of this study was to measure the effect of drinking low-fat milk and an isotonic beverage after intermittent exercise on urine electrolytes. 14 physically active men (23 ± 4 y) were split into two groups: 1) rehydration with isotonic drink (ISO), and 2) rehydration with low-fat milk (LBG). Specific gravity (GEO) and electrolytes (Na+ and K+) were measured in urine before and after exercise with rehydration. Significant differences were found for the GEO and in K+ excretion in the LBG group (p <0.05). Both groups showed significant differences for Na+ excretion concentrations. We conclude that drinking low fat milk after exercise when compared to an isotonic drink, improves GEO and K excretio

The HARPS search for southern extra-solar planets XLI. A dozen planets around the M dwarfs GJ 3138, GJ 3323, GJ 273, GJ 628, and GJ 3293

Context. Low mass stars are currently the best targets for searches for rocky planets in the habitable zone of their host star. Over the last 13 years, precise radial velocities measured with the HARPS spectrograph have identified over a dozen super-Earths and Earth-mass planets (msin i<10Mearth ) around M dwarfs, with a well understood selection function. This well defined sample informs on their frequency of occurrence and on the distribution of their orbital parameters, and therefore already constrains our understanding of planetary formation. The subset of these low-mass planets that were found within the habitable zone of their host star also provide prized targets for future atmospheric biomarkers searches. Aims. We are working to extend this planetary sample to lower masses and longer periods through dense and long-term monitoring of the radial velocity of a small M dwarf sample. Methods. We obtained large numbers of HARPS spectra for the M dwarfs GJ 3138, GJ 3323, GJ 273, GJ 628 and GJ 3293, from which we derived radial velocities (RVs) and spectroscopic activity indicators. We searched them for variabilities, periodicities, Keplerian modulations and correlations, and attribute the radial-velocity variations to combinations of planetary companions and stellar activity. Results. We detect 12 planets, of which 9 are new with masses ranging from 1.17 to 10.5 Mearth . Those planets have relatively short orbital periods (P<40 d), except two of them with periods of 217.6 and 257.8 days. Among these systems, GJ 273 harbor two planets with masses close to the one of the Earth. With a distance of 3.8 parsec only, GJ 273 is the second nearest known planetary system - after Proxima Centauri - with a planet orbiting the circumstellar habitable zone.Comment: 19 pages, 24 figures. Astronomy and Astrophysics in pres

Evolutionary algorithm for timber shelter optimization

The present paper describes an approach to wood as an alternative construction material and the formal search of typologies which combine a secure and efficient structure with an architectural based definition of dimensions and geometry. The outcome, given by a genetic algorithm is intended to be used as a concept to develop shelter solutions for the village of Jametla, located on the coast of the state of Jalisco, in Mexico

Nuevas ocurrencias y descripción del hábitat de la rana endémica del sur de Ecuador Atelopus exiguus (Anura: Bufonidae) en un punto crítico de conservación en los altos Andes

Atelopus species are classified as a priority taxon for monitoring and conservation, of these A. exiguus is endemic to southern Ecuador and is classified as critically endangered, however, within its known geographic range, little attention has been given to identifying new localities particularly across the páramo ecosystem (&gt; 3500 m a.s.l.). Therefore, in the páramo landscape of Macizo del Cajas Biosphere Reserve, a conservation hotspot, we intensively searched for A. exiguus across 15 localities (elevation range: 3550 – 3800 m a.s.l.). In one year of monitoring (2020 – 2021), we recorded four individuals of A. exiguus (two were tadpoles) in two localities. The localities are characterized by a higher proportion of páramo grassland in association with shrubby páramo as well as cushion páramo; this riparian habitat is related to relatively good water quality (according to Andean Biotic Index), relatively low water temperatures and relatively low water flow. Our findings, accompanied by a detailed monitoring protocol, suggest habitat requirements for A. exiguus. Further intensive surveys beyond the limits of protected areas of Azuay province, especially across the páramos, is emerging as an urgent step to improve conservation decisions.Las especies del género Atelopus están clasificadas como un taxón prioritario para su monitoreo y conservación, de ellas A. exiguus es endémica del sur de Ecuador y está clasificada como en peligro crítico de extinción. Sin embargo, dentro de su área de distribución geográfica conocida, poca atención se ha prestado en identificar nuevas localidades, especialmente en el ecosistema del páramo (&gt; 3500 m de altitud). Por lo tanto, en el paisaje de páramo de la Reserva de la Biosfera Macizo del Cajas, un punto caliente de conservación, buscamos intensamente la especie en 15 localidades (rango de elevación: 3550 – 3800 m de altitud). En un año de monitoreo (2020 – 2021), registramos cuatro individuos de A. exiguus (dos fueron renacuajos) en dos localidades. Las localidades se caracterizan por una mayor proporción de pastizales de páramo en asociación con páramo arbustivo, así como páramo de almohadilla; este hábitat ribereño está relacionado con una calidad de agua relativamente buena (según el Índice Biótico Andino), temperaturas de agua relativamente bajas, así como un flujo de agua relativamente bajo. Nuestros hallazgos, acompañados de un protocolo de monitoreo detallado, sugieren los requerimientos de hábitat para A. exiguus. La realización de más estudios intensivos más allá de los límites de las áreas protegidas de la provincia de Azuay, especialmente a través de los páramos, se considera como urgente para mejorar las decisiones de conservación

Strong HI Lyman-α\alpha variations from the 11 Gyr-old host star Kepler-444: a planetary origin ?

Kepler-444 provides a unique opportunity to probe the atmospheric composition and evolution of a compact system of exoplanets smaller than the Earth. Five planets transit this bright K star at close orbital distances, but they are too small for their putative lower atmosphere to be probed at optical/infrared wavelengths. We used the Space Telescope Imaging Spectrograph instrument onboard the Hubble Space Telescope to search for the signature of the planet's upper atmospheres at six independent epochs in the Ly-$\alpha$ line. We detect significant flux variations during the transits of both Kepler-444e and f (~20%), and also at a time when none of the known planets was transiting (~40%). Variability in the transition region and corona of the host star might be the source of these variations. Yet, their amplitude over short time scales (~2-3 hours) is surprisingly strong for this old (11.2+-1.0Gyr) and apparently quiet main-sequence star. Alternatively, we show that the in-transits variations could be explained by absorption from neutral hydrogen exospheres trailing the two outer planets (Kepler-444e and f). They would have to contain substantial amounts of water to replenish such hydrogen exospheres, which would reveal them as the first confirmed ocean-planets. The out-of-transit variations, however, would require the presence of a yet-undetected Kepler-444g at larger orbital distance, casting doubt on the planetary origin scenario. Using HARPS-N observations in the sodium doublet, we derived the properties of two Interstellar Medium clouds along the line-of-sight toward Kepler-444. This allowed us to reconstruct the stellar Ly-$\alpha$ line profile and to estimate the XUV irradiation from the star, which would still allow for a moderate mass loss from the outer planets after 11.2Gyr. Follow-up of the system at XUV wavelengths will be required to assess this tantalizing possibility.Comment: Accepted for publication in A&A Name of the system added to the title in most recent versio

The HARPS search for southern extra-solar planets XXXV. Planetary systems and stellar activity of the M dwarfs GJ 3293, GJ 3341, and GJ 3543

Context. Planetary companions of a fixed mass induce larger amplitude reflex motions around lower-mass stars, which helps make M dwarfs excellent targets for extra-solar planet searches. State of the art velocimeters with $\sim$1m/s stability can detect very low-mass planets out to the habitable zone of these stars. Low-mass, small, planets are abundant around M dwarfs, and most known potentially habitable planets orbit one of these cool stars. Aims. Our M-dwarf radial velocity monitoring with HARPS on the ESO 3.6m telescope at La Silla observatory makes a major contribution to this sample. Methods. We present here dense radial velocity (RV) time series for three M dwarfs observed over $\sim5$ years: GJ 3293 (0.42M$_\odot$), GJ 3341 (0.47M$_\odot$), and GJ 3543 (0.45M$_\odot$). We extract those RVs through minimum $\chi^2$ matching of each spectrum against a high S/N ratio stack of all observed spectra for the same star. We then vet potential orbital signals against several stellar activity indicators, to disentangle the Keplerian variations induced by planets from the spurious signals which result from rotational modulation of stellar surface inhomogeneities and from activity cycles. Results. Two Neptune-mass planets - $msin(i)=1.4\pm0.1$ and $1.3\pm0.1M_{nept}$ - orbit GJ 3293 with periods $P=30.60\pm0.02$ d and $P=123.98\pm0.38$ d, possibly together with a super-Earth - $msin(i)\sim7.9\pm1.4M_\oplus$ - with period $P=48.14\pm0.12\;d$. A super-Earth - $msin(i)\sim6.1M_\oplus$ - orbits GJ 3341 with $P=14.207\pm0.007\;d$. The RV variations of GJ 3543, on the other hand, reflect its stellar activity rather than planetary signals.Comment: Accepted for publication in A&A, 19 pages, 12 figures, 7 table