The effect of magnetic activity on low-mass stars in eclipsing binaries

In recent years, analyses of eclipsing binary systems have unveiled differences between the observed fundamental properties of low-mass stars and those predicted by stellar structure models. Particularly, radius and effective temperatures computed from models are ~ 5-10% lower and ~ 3-5% higher than observed, respectively. These discrepancies have been attributed to different factors, notably to the high levels of magnetic activity present on these stars. In this paper, we test the effect of magnetic activity both on models and on the observational analysis of eclipsing binaries using a sample of such systems with accurate fundamental properties. Regarding stellar models, we have found that unrealistically high spot coverages need to be assumed to reproduce the observations. Tests considering metallicity effects and missing opacities on models indicate that these are not able to explain the radius discrepancies observed. With respect to the observations, we have tested the effect of several spot distributions on the light curve analysis. Our results show that spots cause systematic deviations on the stellar radii derived from light curve analysis when distributed mainly over the stellar poles. Assuming the existence of polar spots, overall agreement between models and observations is reached when ~ 35% spot coverage is considered on stellar models. Such spot coverage induces a systematic deviation in the radius determination from the light curve analysis of ~ 3% and is also compatible with the modulations observed on the light curves of these systems. Finally, we have found that the effect of activity or rotation on convective transport in partially radiative stars may also contribute to explain the differences seen in some of the systems with shorter orbital periods.Comment: 12 pages, 9 figures, accepted for publication in Ap

Beliefs and understandings of assessment theories and terminologies by university lecturers

This study investigated the beliefs and practices of university lecturers around assessment theories and their links with teaching practices. Given the discrepancies in the literature, the research explored the gap in theoretical understandings of summative and formative assessment and the relationship between them, as well as the relationship with lecturers’ own practices. In total, 109 lecturers from a Colombian institution of higher education participated. An instrument consisting mainly of quantitative questions, with some qualitative questions, which was originally designed to investigate these beliefs and practices among higher education lecturers in England, was used. The translation, validation and reliability processes of the instrument were carried out. Thus, an exploratory factorial study was performed to establish the dimensions of the instrument, determining seven factors. The results indicate discrepancies between what lecturers understand by formative and summative assessment and their practices in the classroom

Evaluación de ambientes virtuales de aprendizaje. Una gestión para mejorar

This paperdesigns an instrument (in Checklist format) to evaluate any platform as a Virtual Learning Environment (VLE) and shows the results of the evaluation of a learning environment through this instrument, in this case, the analyzed environment are the spaces that the Virtual Learning Environment of the Department of Virtual Education of the University of Granma (Cuba) has. The instrument is designed in response to four spaces or general indicators: Information Space, Mediation/Interaction Space, Instructional Design Space and Exhibition Space, in order to identify weaknesses to take actions towards the improvement of the platform and virtual interaction between the advisor and the students, and create strategies that help to reduce or eliminate them to contribute to the improvement of courses designed for virtual learning environments.Este artículo diseña un instrumento (en formato Lista de cotejo) para evaluar cualquier plataforma como un Ambiente Virtual de Aprendizaje (AVA) y muestra los resultados de la evaluación de un ambiente de aprendizaje a través de este instrumento, en este caso, el ambiente analizado son los espacios con los que cuenta el Ambiente Virtual de Aprendizaje del Departamento de Educación Virtual de la Universidad de Granma (Cuba). El instrumento se diseña respondiendo a cuatro espacios o indicadores generales: Espacio de Información, Espacio de Mediación/Interacción, Espacio de Diseño Instruccional y Espacio de Exhibición, con el fin de identificar debilidades para tomar acciones hacia la mejora de la plataforma y la interacción virtual entre el asesor y los alumnos, y crear estrategias que ayuden a aminorarlas o eliminarlas para contribuir a la mejora de los cursos diseñados para ambientes virtuales de aprendizaje.Universidad Pablo de Olavid

Depressed excitability and ion currents linked to slow exocytotic fusion pore in chromaffin cells of the SOD1(G93A) mouse model of amyotrophic lateral sclerosis

Altered synaptic transmission with excess glutamate release has been implicated in the loss of motoneurons occurring in amyotrophic lateral sclerosis (ALS). Hyperexcitability or hypoexcitability of motoneurons from mice carrying the ALS mutation SOD1G93A (mSOD1) has also been reported. Here we have investigated the excitability, the ion currents, and the kinetics of the exocytotic fusion pore in chromaffin cells from postnatal day 90 to postnatal day 130 mSOD1 mice, when motor deficits are already established. With respect to wild-type (WT), mSOD1 chromaffin cells had a decrease in the following parameters: 95% in spontaneous action potentials, 70% in nicotinic current for acetylcholine (ACh), 35% in Na+ current, 40% in Ca2+-dependent K+ current, and 53% in voltage-dependent K+ current. Ca2+ current was increased by 37%, but the ACh-evoked elevation of cytosolic Ca2+ was unchanged. Single exocytotic spike events triggered by ACh had the following differences (mSOD1 vs. WT): 36% lower rise rate, 60% higher decay time, 51% higher half-width, 13% lower amplitude, and 61% higher quantal size. The expression of the α3-subtype of nicotinic receptors and proteins of the exocytotic machinery was unchanged in the brain and adrenal medulla of mSOD1, with respect to WT mice. A slower fusion pore opening, expansion, and closure are likely linked to the pronounced reduction in cell excitability and in the ion currents driving action potentials in mSOD1, compared with WT chromaffin cells.This work was funded by: (1) SAF-2010-21795, MINECO; (2) SAF-2010-792 18837, MINECO; (3) CABICYC, UAM/Bioibérica; (4) Fundación Teófilo 793 Hernando, Madrid, Spai

Absolute properties of the low-mass eclipsing binary CM Draconis

Spectroscopic and eclipsing binary systems offer the best means for determining accurate physical properties of stars, including their masses and radii. The data available for low-mass stars have yielded firm evidence that stellar structure models predict smaller radii and higher effective temperatures than observed, but the number of systems with detailed analyses is still small. In this paper we present a complete reanalysis of one of such eclipsing systems, CM Dra, composed of two dM4.5 stars. New and existing light curves as well as a radial velocity curve are modeled to measure the physical properties of both components. The masses and radii determined for the components of CM Dra are M1=0.2310+/-0.0009 Msun, M2=0.2141+/-0.0010 Msun, R1=0.2534+/-0.0019 Rsun, and R2=0.2396+/-0.0015 Rsun. With relative uncertainties well below the 1% level, these values constitute the most accurate properties to date for fully convective stars. This makes CM Dra a valuable benchmark for testing theoretical models. In comparing our measurements with theory, we confirm the discrepancies reported previously for other low-mass eclipsing binaries. These discrepancies seem likely to be due to the effects of magnetic activity. We find that the orbit of this system is slightly eccentric, and we have made use of eclipse timings spanning three decades to infer the apsidal motion and other related properties.Comment: 19 pages, 9 figures. Accepted for publication in Ap

Effectiveness of a hydrophobic dressing for microorganisms’ colonization of vascular ulcers: Protocol for a randomized controlled trial (CUCO-UV Study)

Aim: To determine the effectiveness of a hydrophobic dressing (Cutimed Sorbact® ) against a silver dressing (Aquacel® Ag Extra) in the level of colonization of chronic venous leg ulcers. The secondary endpoints are health-related quality of life, level of pain, and time to complete healing. Design: Open randomized controlled trial, with blinded endpoint. Methods: Patients with chronic venous leg ulcers with signs of critical colonization will be randomized in a concealed sequence using computer software to receive one of the alternative dressings. A total of 204 participants recruited in Primary Health Care and nursing homes will be necessary to assure statistical power. Measures will include sociodemographic variables, wound-related variables (area, exudate, and time to healing), level of pain, adverse effects, and health-related quality of life. Smear samples will be collected from the ulcers and will be subject to DNA-typing technique through polymerase chain reaction to obtain the level of colony-forming units. Measures will be collected at baseline, 4, 8, and 12 weeks. Discussion: Elevated levels of microorganisms prevent wound healing and favour its chronification. The main target when colonization is present is to reduce the bacterial load to levels that promote immune system mobilization. Hydrophobic dressings prevent the formation of biofilm in the wound by means of physical effect, so that the possibility of antimicrobial resistance is significantly reduced. Impact: Current evidence about the effectiveness of dressings to minimize venous leg ulcers colonization is very limited. Previous studies have important methodological flaws. This study will permit to obtain the effectiveness of hydrophobic dressings against silver dressings with a robust design based on conditions of routine clinical practice in Primary Health Care and nursing homes

A comparison of feature extractors for panorama stitching in an autonomous car architecture.

Panorama stitching consists on frames being put together to create a 360o view. This technique is proposed for its implementation in autonomous vehicles instead of the use of an external 360o camera, mostly due to its reduced cost and improved aerodynamics. This strategy requires a fast and robust set of features to be extracted from the images obtained by the cameras located around the inside of the car, in order to effectively compute the panoramic view in real time and avoid hazards on the road. In this paper, we compare and discuss three feature extraction methods (i.e. SIFT, BRISK and SURF) for image feature extraction, in order to decide which one is more suitable for a panorama stitching application in an autonomous car architecture. Experimental validation shows that SURF exhibits an improved performance under a variety of image transformations, and thus appears to be the most suitable of these three methods, given its accuracy when comparing features between both images, while maintaining a low time consumption. Furthermore, a comparison of the results obtained with respect to similar work allows to increase the reliability of our methodology and the reach of our conclusions

Thermodynamic Parameters of Adsorption from Systems Activated Carbon Chlordiazepoxide and Activated Carbon-Diazepam Parámetros termodinámicos de adsorción de los sistemas carbón activado-clordiazepóxido y carbón activado-diazepam

Resumen Se estudian los parámetros termodinámicos de la adsorción de clordiazepóxido y diazepam en seis carbonos activados: Norit B, BDH, Merck, Panreac, M1 y M, en fluido gástrico simulado. Los materiales se caracterizan por: FTIR, pHzpc y adsorción de N 2 a 77 K. La porosidad fue interpretada por las ecuaciones de Dubinin-Radushkevich y BET. Los resultados muestran la relación entre el aumento de la temperatura, las características de cada adsorbente y el comportamiento de estos fármacos. Los valores positivos de todas las entalpías isostéricas de adsorción determinadas a partir de la pendiente de Van 't Hoff (R 2 > 97), indican la naturaleza endotérmica del proceso de adsorción, así como la ∆G < 0 con el incremento de la temperatura. La ∆G < 0 en todos los casos explica el carácter espontáneo del proceso de adsorción. Los valores positivos ∆S dejan claramente que la aleatoriedad se incrementó en la interfaz sólido-solución durante el proceso de adsorción. Palabras clave: carbón activado, adsorción, parámetros termodinámicos. Abstract It is study the thermodynamic parameters of chlordiazepoxide and diazepam drugs adsorbed onto six activated carbons: Norit B, BDH, Merck, Panreac, M1 and M, from simulated gastric fluid at pH 1,2 for 4 h were characterized by FTIR, pH zpc, and adsorption of N 2 to 77 K. The results of porosity were interpreted with the Dubinin-Radushkevich's models and BET' equation. By UV visible spectra residual drugs were monitored. The results show relationship between: increased of temperature, the characteristics of each adsorbent and the behavior of these drugs in acid solution. The positive values of all the isosteric adsorption enthalpies determined from the slope Van't Hoff plot (R 2 > 97), indicate the nature endothermic process of adsorption. The ∆G<0 in all cases explained the spontaneous character of the adsorption process and the positive values of ∆S state clearly that the randomness increased at the solidsolution interface during adsorption process

Perspectivas de la empresa y la economía mexicana frente a la reestructuración productiva

1 archivo PDF (404 páginas)Este texto se presenta una reflexión de investigadores de la UAM, así como de otras Instituciones de Educación Superior respecto al marco en el que se han desenvuelto las empresas mexicanas en los últimos años, así como del desarrollo en algunos de sus sistemas organizacionales. PALABRAS CLAVE: Mexico Economic policy 1970-1994