305 research outputs found
Culture of paso de la amada, creator of ‘mesoamerican ballgame’
Se realiza una revisión sobre el origen del juego de pelota mesoamericano en el preclásico temprano (ca.1.700-1.000 a.C.). Por la antigüedad propuesta para sus vestigios sobre el juego de pelota, son candidatos a ser los ‘creadores del juego’ las culturas de Paso de la Amada, los pre-olmecas de San Lorenzo y El Opeño. Los vestigios referidos son fundamentalmente, la cancha de Paso de la Amada, las pelotas de hule de Manatà y las figurillas de El Opeño.
Se concluye que la gran cancha de Paso de la Amada, la mayor construcción de Mesoamérica de su tiempo, aparece como el vestigio más antiguo del juego, y se le relaciona con la aparición de la primera sociedad no igualitaria en Mesoamérica. Se sugiere que los pobladores de Paso de la Amada, hacia 1650 a.C., fueron los creadores del juego y no los olmecas como generalmente se ha defendidoWe study here the origin of the Mesoamerican ballgame during the early formative period (ca. 1700 B.C.). We select as candidates for the creators of the Mesoamerican ballgame the cultures of Paso de la Amada, pre-Olmec at San Lorenzo, and El Opeño, as they have the oldest vestiges of the ballgame. These vestiges are, to be exact, a ball court at Paso de la Amada, some rubber balls at Manati, and ceramic figurines at El Opeño.
We conclude that the great ball court at Paso de la Amada, the biggest building of Mesoamerica at that time, appears as the oldest vestige of the game and it is in relation with the emergence of ranked societies in Mesoamerica. We suggest that the people of Paso de la Amada, around 1650 BC, were the creators of the game, and not the Olmecs, as generally defende
Struggles and pacification in the history of american kinesiology
En este artÃculo estudiamos la disputa epistemológica y pedagógica sobre la kinesiologÃa/educación fÃsica que ha tenido lugar en las universidades de Estados Unidos desde 1990 hasta la actualidad. Hemos recogido el pensamiento de una muestra amplia de autores involucrados, con el propósito de obtener una visión de conjunto de un proceso que, de acuerdo con Morrow (2006), trata de esclarecer ¿de dónde venimos?, ¿qué somos?, ¿a dónde vamos? Tras el cotejo y análisis de la documentación más relevante concluimos que el periodo 1990-2013, caracterizado por una enconada pugna de paradigmas –en la que han estado implicados humanistas, positivistas, crosdisciplinaristas y subdisciplinaristas–, ha dado como resultado el dominio del paradigma integrador de Kretchmar (2007, 2008)In this article we review the epistemological and pedagogical debate on Kinesiology and Physical Education that has been going on in the universities of the US from 1990 to the present. We have compiled the opinions of a wide sample of authors, with the intention of getting the most complete picture of a process that, according to Morrow (2006), seeks to answer the questions "where we come from, who we are, and where we are going". After comparing and analysing the most relevant documents, we conclude that the period 1990-2013, characterized by a bitter struggle between paradigms fought by humanists, positivists, cross-disciplinarists, and sub-disciplinarists, has revealed the eventual predominance of the integrative paradigm of Kretchmar (2007, 2008
Line-Strength Indices in Bright Spheroidals: Evidence for a Stellar Population Dichotomy between Spheroidal and Elliptical Galaxies
We present new measurements of central line-strength indices (namely Mg2,
, and Hbeta and gradients for a sample of 6 bright spheroidal galaxies
(Sph's) in the Virgo cluster. Comparison with similar measurements for
elliptical galaxies (E's), galactic globular clusters (GGC's), and stellar
population models yield the following results: (1) In contrast with bright E's,
bright Sph's are consistent with solar abundance [Mg/Fe] ratios; (2) Bright
Sph's exhibit metallicities ranging from values typical for metal-rich GGC's to
those for E's; (3) Although absolute mean ages are quite model dependent, we
find evidence that the stellar populations of some (if not all) Sph's look
significantly younger than GGC's; and (4) Mg2 gradients of bright Sph's are
significantly shallower than those of E galaxies. We conclude that the
dichotomy found in the structural properties of Sph and E galaxies is also
observed in their stellar populations. A tentative interpretation in terms of
differences in star formation histories is suggested.Comment: 14 pages, LaTeX file + 2 PostScript figures, aasms4.sty require
CAFE: Calar Alto Fiber-fed Echelle spectrograph
We present here CAFE, the Calar Alto Fiber-fed Echelle spectrograph, a new
instrument built at the Centro Astronomico Hispano Alem\'an (CAHA). CAFE is a
single fiber, high-resolution (70000) spectrograph, covering the
wavelength range between 3650-9800\AA. It was built on the basis of the common
design for Echelle spectrographs. Its main aim is to measure radial velocities
of stellar objects up to 13-14 mag with a precision as good as a few
tens of . To achieve this goal the design was simplified at maximum,
removing all possible movable components, the central wavelength is fixed, so
the wavelentgth coverage; no filter wheel, one slit and so on, with a
particular care taken in the thermal and mechanical stability. The instrument
is fully operational and publically accessible at the 2.2m telescope of the
Calar Alto Observatory.
In this article we describe (i) the design, summarizing its manufacturing
phase; (ii) characterize the main properties of the instrument; (iii) describe
the reduction pipeline; and (iv) show the results from the first light and
commissioning runs. The preliminar results indicate that the instrument fulfill
the specifications and it can achieve the foreseen goals. In particular, they
show that the instrument is more efficient than anticipated, reaching a
20 for a stellar object as faint as 14.5 mag in 2700s
integration time. The instrument is a wonderful machine for exoplanetary
research (by studying large samples of possible systems cotaining massive
planets), galactic dynamics (high precise radial velocities in moving groups or
stellar associations) or astrochemistry.Comment: 12 pages, 23 figures; Acepted for publishing in A&A, 201
Excipient-free inhalable microparticles of Azithromycin produced by electrospray: A novel approach to direct pulmonary delivery of antibiotics
Inhalation therapy offers several advantages in respiratory disease treatment. Azithromycin is a macrolide antibiotic with poor solubility and bioavailability but with a high potential to be used to fight lung infections. The main objective of this study was to generate a new inhalable dry powder azithromycin formulation. To this end, an electrospray was used, yielding a particle size around 2.5 µm, which is considered suitable to achieve total deposition in the respiratory system. The physicochemical properties and morphology of the obtained microparticles were analysed with a battery of characterization techniques. In vitro deposition assays were evaluated after aerosolization of the powder at constant flow rate (100 L/min) and the consideration of the simulation of two different realistic breathing profiles (healthy and chronic obstructive pulmonary disease (COPD) patients) into a next generation impactor (NGI). The formulation was effective in vitro against two types of bacteria, Staphylococcus aureus and Pseudomonas aeruginosa. Finally, the particles were biocompatible, as evidenced by tests on the alveolar cell line (A549) and bronchial cell line (Calu-3). © 2021 by the authors. Licensee MDPI, Basel, Switzerland
Internal Kinematics of Luminous Compact Blue Galaxies
We describe the dynamical properties which may be inferred from HST/STIS
spectroscopic observations of luminous compact blue galaxies (LCBGs) between
0.1<z<0.7. While the sample is homogeneous in blue rest-frame color, small size
and line-width, and high surface-brightness, their detailed morphology is
eclectic. Here we determine the amplitude of rotation versus random, or
disturbed motions of the ionized gas. This information affirms the accuracy of
dynamical mass and M/L estimates from Keck integrated line-widths, and hence
also the predictions of the photometric fading of these unusual galaxies. The
resolved kinematics indicates this small subset of LCBGs are dynamically hot,
and unlikely to be embedded in disk systems.Comment: To appear in "Starbursts: from 30 Doradus to Lyman Break Galaxies"
2005, eds. R. de Grijs and R. M. Gonzalez Delgado (Kluwer
Using spectroscopic data to disentangle stellar population properties
It is well known that, when analyzed in the light of current synthesis model predictions, variations in the physical properties of single stellar populations (e.g. age, metallicity, initial mass function, element abundance ratios) may have a similar effect in their integrated spectral energy distributions. The confusion is even worsened when more realistic scenarios, i.e. composite star formation histories, are considered. This is, in fact, one of the major problems when facing the study of stellar populations in star clusters and galaxies. Typically, the observational efforts have aimed to find the most appropriate spectroscopic indicators in order to avoid, as far as possible, degeneracies in the parameter space. However, from a practical point of view, the most suited observables are not, necessarily, those that provide more orthogonality in that parameter space, but those that give the best balance between parameter degeneracy and sensitivity to signal-to-noise ratio per Angstrom, S/N(Angstrom). In order to achieve the minimum combined total error in the derived physical parameters, this work discusses how the functional dependence of typical line-strength indices and colors on S/N(Angstrom) allows to define a suitability parameter which helps to obtain more realistic combinations of spectroscopic data. As an example, we discuss in more detail the problem of breaking the well known age-metallicity degeneracy in relatively old stellar populations, comparing the suitability of different spectroscopic diagrams for a simple stellar population of solar metallicity and of 12 Gyr in age
The CARMENES search for exoplanets around M dwarfs - Photospheric parameters of target stars from high-resolution spectroscopy
The new CARMENES instrument comprises two high-resolution and high-stability
spectrographs that are used to search for habitable planets around M dwarfs in
the visible and near-infrared regime via the Doppler technique. Characterising
our target sample is important for constraining the physical properties of any
planetary systems that are detected. The aim of this paper is to determine the
fundamental stellar parameters of the CARMENES M-dwarf target sample from
high-resolution spectra observed with CARMENES. We also include several M-dwarf
spectra observed with other high-resolution spectrographs, that is CAFE, FEROS,
and HRS, for completeness. We used a {chi}^2 method to derive the stellar
parameters effective temperature T_eff, surface gravity log g, and metallicity
[Fe/H] of the target stars by fitting the most recent version of the
PHOENIX-ACES models to high-resolution spectroscopic data. These stellar
atmosphere models incorporate a new equation of state to describe spectral
features of low-temperature stellar atmospheres. Since T_eff, log g, and [Fe/H]
show degeneracies, the surface gravity is determined independently using
stellar evolutionary models. We derive the stellar parameters for a total of
300 stars. The fits achieve very good agreement between the PHOENIX models and
observed spectra. We estimate that our method provides parameters with
uncertainties of {sigma} T_eff = 51 K, {sigma} log g = 0.07, and {sigma} [Fe/H]
= 0.16, and show that atmosphere models for low-mass stars have significantly
improved in the last years. Our work also provides an independent test of the
new PHOENIX-ACES models, and a comparison for other methods using
low-resolution spectra. In particular, our effective temperatures agree well
with literature values, while metallicities determined with our method exhibit
a larger spread when compared to literature results
Tunable injectable alginate-based hydrogel for cell therapy in Type 1 Diabetes Mellitus
Islet transplantation has the potential of reestablishing naturally-regulated insulin production in Type 1 diabetic patients. Nevertheless, this procedure is limited due to the low islet survival after transplantation and the lifelong immunosuppression to avoid rejection. Islet embedding within a biocompatible matrix provides mechanical protection and a physical barrier against the immune system thus, increasing islet survival. Alginate is the preferred biomaterial used for embedding insulin-producing cells because of its biocompatibility, low toxicity and ease of gelation. However, alginate gelation is poorly controlled, affecting its physicochemical properties as an injectable biomaterial. Including different concentrations of the phosphate salt Na2HPO4 in alginate hydrogels, we can modulate their gelation time, tuning their physicochemical properties like stiffness and porosity while maintaining an appropriate injectability. Moreover, these hydrogels showed good biocompatibility when embedding a rat insulinoma cell line, especially at low Na2HPO4 concentrations, indicating that these hydrogels have potential as injectable biomaterials for Type 1 Diabetes Mellitus treatment
Influence of data sources and processing methods on theoretical river network quality
Stream ecosystem research and water resource management need to be considered over broad spatial scales. Moreover, the investigation of the spatial configuration and habitat characteristics of streams requires an accurate and precise spatial framework to reflect a catchment's physical reality that can successfully explain observed patterns at smaller scales. In this sense, geographic information systems represent an essential tool to satisfy the needs of researchers and managers. Specifically, theoretical river networks (TRNs) extracted from digital elevation models (DEMs) have become much more common in recent years, as they can provide a suitable spatial network and hierarchical organisation to sort out river ecosystem information from reach to catchment levels. Nevertheless the quality of the extracted TRN depends greatly on the spatial resolution of the DEM and the methodology used in the network extraction processes. In this study, we compare the quality of 9 TRNs extracted from DEMs with different spatial resolutions ranging from regional (5 m) to national (25 m) and global scales (90 m) using the ArcHydro, Hec-GeoHMS and Netstream software packages. To achieve our goal, we compared (i) the DEM-derived slope; (ii) the spatial accuracy of the TRNs in relation to a control river network; (iii) the structure of the TRNs through analysis of the number of river segments, average river segment length and total river length by stream order, drainage density and the mean upstream slope throughout the TRN; and (iv) the ability of variables derived from TRNs to discriminate among stream types classified according to flow type and substrate composition. We demonstrated that not only DEM spatial resolution but also the DEM data source and raster creation process exert an important influence on terrain characteristics derived from DEMs and TRN properties. Moreover, TRNs extracted with NetStream generally showed better performance than those extracted with ArchHydro and HecGeoHMS. Nevertheless, river network extraction quality, DEM spatial resolution and extraction algorithms exhibit complex relationships due to the large number of interacting factors.La investigación de los ecosistemas acuáticos continentales y la gestión de recursos hÃdricos necesitan ser considerados a escalas espaciales que abarquen grandes territorios. Asà mismo, el estudio de la configuración espacial de los sistemas fluviales y las caracterÃsticas del hábitat requieren de un marco espacial preciso con el que explicar los patrones observados a pequeña escala a partir de las caracterÃsticas fÃsicas de la cuenca. En este sentido, los sistemas de información geográfica representan una herramienta esencial. EspecÃficamente, la extracción de redes fluviales teóricas (RFT) a partir de modelos digitales de elevación (MDEs) ha sufrido una importante expansión y desarrollo en los últimos años. Las RTF, proporcionan un marco espacial adecuado e integran la estructura jerárquica de los ecosistemas fluviales, de tal modo que pueden englobar información a diferentes escales espaciales, desde el nivel de cuenca al de tramo. Sin embargo, la calidad de las RFTs depende, en gran medida, de la resolución espacial de los MDE y de los métodos utilizados en el proceso de extracción de la red. En este estudio hemos comparado la calidad de 9 RFTs obtenidas a partir de MDEs con diferentes resoluciones espaciales, que van desde la escala regional (5 m), nacional (25 m) hasta global (90 m) mediante ArcHydro, HecGeoHMS y NetStream.Para lograr nuestro objetivos hemos comparado (i) las caracterÃsticas de la pendiente derivada de los MDEs, (ii) la precisión espacial de las RFT en relación a una red fluvial control, (iii) la estructura de los RTFs mediante el análisis del número de segmentos, la longitud media y total de los segmentos de cada orden fluvial, la densidad de drenaje y la pendiente media de la cuenca a lo largo de la RFT y (iv) la capacidad de variables fÃsicas derivadas de las RFT para discriminar entre tipos de rÃos clasificados con base en el tipo de flujo y la composición del sustrato. Los resultados obtenidos han demostrado que la calidad de las caracterÃsticas fÃsicas derivadas del MDE y las propiedades de las RFTs no están determinadas únicamente por la resolución espacial del MDE, sino que el tipo de dato del que provenga el MDE y el proceso de generación del mismo ejercen una gran influencia. Además, NetStream ha generado, por lo general, unas RTFs más precisas que ArcHydro y HecGeoHMS. Sin embargo, la interacción de un gran número de factores durante el proceso de generación de redes hace que las relaciones entre la calidad de las mismas, la resolución espacial de los MDE y los algoritmos utilizados sean complejas
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