The acoustic cut-off frequency of the Sun and the solar magnetic activity cycle

The acoustic cut-off frequency -the highest frequency for acoustic solar eigenmodes- is an important parameter of the solar atmosphere as it determines the upper boundary of the p-mode resonant cavities. At frequencies beyond this value, acoustic disturbances are no longer trapped but traveling waves. Interference amongst them give rise to higher-frequency peaks -the pseudomodes- in the solar acoustic spectrum. The pseudomodes are shifted slightly in frequency with respect to p modes making possible the use of pseudomodes to determine the acoustic cut-off frequency. Using data from GOLF and VIRGO instruments on board the SOHO spacecraft, we calculate the acoustic cut-off frequency using the coherence function between both the velocity and intensity sets of data. By using data gathered by these instruments during the entire lifetime of the mission (1996 till the present), a variation in the acoustic cut-off frequency with the solar magnetic activity cycle is found.Comment: Paper accepted in ApJ. 26 Pages, 9 figure

The onset of solar cycle 24: What global acoustic modes are telling us

We study the response of the low-degree, solar p-mode frequencies to the unusually extended minimum of solar surface activity since 2007. A total of 4768 days of observations collected by the space-based, Sun-as-a-star helioseismic GOLF instrument are analyzed. A multi-step iterative maximum-likelihood fitting method is applied to subseries of 365 days and 91.25 days to extract the p-mode parameters. Temporal variations of the l=0, 1, and 2 p-mode frequencies are then obtained from April 1996 to May 2009. While the p-mode frequency shifts are closely correlated with solar surface activity proxies during the past solar cycles, the frequency shifts of the l=0 and l=2 modes show an increase from the second half of 2007, when no significant surface activity is observable. On the other hand, the l=1 modes follow the general decreasing trend of the solar surface activity. The different behaviours between the l=0 and l=2 modes and the l=1 modes can be interpreted as different geometrical responses to the spatial distribution of the solar magnetic field beneath the surface of the Sun. The analysis of the low-degree, solar p-mode frequency shifts indicates that the solar activity cycle 24 started late 2007, despite the absence of activity on the solar surface.Comment: To be accepted by A&A (with minor revisions), 4 pages, 3 figures, 1 tabl

An infrared study of galactic OH/IR stars. I. An optical/near-IR atlas of the Arecibo sample

In this paper we present optical and near-infrared finding charts, accurate astrometry (~1") and single-epoch near-infrared photometry for 371 IRAS sources, 96% of those included in the so-called Arecibo sample of OH/IR stars (Eder et al. 1988; Lewis et al. 1990a; Chengalur et al. 1993). The main photometric properties of the stars in the sample are presented and discussed as well as the problems found during the process of identification of the optical/near-infrared counterparts. In addition, we also identify suitable reference stars in each field to be used for differential photometry purposes in the future. We find that 39% of the sources (144 in number) have no optical counterpart, 8 of them being invisible even at near infrared wavelengths. The relative distribution of sources with and without optical counterpart in the IRAS two-colour diagram and their characteristic near infrared colours are interpreted as the consequence of the increasing thickness of their circumstellar shells. Among the objects not detected at near infrared wavelengths four non-variable sources are proposed to be heavily obscured post-AGB stars which have just very recently left the AGB. Eight additional objects with unusually bright and/or blue near-infrared colours are identified as candidate post-AGB stars and/or proto-planetary nebulae.Comment: 28 pages, 9 figures, for associated finding charts see: http://www.edpsciences.org/articles/aa/full/2005/08/aa1709/FINDING_CHARTS/are cibo_index.htm

Intensity of physical education classes in adolescents

Se registró la frecuencia cardiaca de 182 estudiantes (97 chicos y 85 chicas) de entre 12 y 18 años durante sus clases de Educación Física. Los resultados muestran una media del 21,62±14,33% del tiempo de clase en valores MVPA (moderate to vigorous physical activity). Respecto al género, pese a no ser significativo, los mayores valores corresponden a la chicas (23,47±14,45% vs 19,99±14,10%; p=0,106). No se ha observado efecto del tipo de sesión (deportes colectivos, deportes individuales, juegos tradicionales o bailes) sobre el tiempo en valores MVPA (p>0,05; TE0.05; ES<0.020), obtaining the highest values in team sports sessions. Results show that intensity and duration of analyzed classes do not comply with recommendations to become an adequate cardiovascular exercis

Photoionization-ion mobility spectrometer for non-targeted screening analysis or for targeted analysis coupling a Tenax TA column

Photoionization-ion mobility spectrometer (UV-IMS) can be used as a screening instrument to distinguish gasoline vapors from other similar samples, obtaining characteristic fingerprints in a quick and simple analysis. A non-targeted approach can be used to resolve many problems, moreover, this device can also be used for targeted analysis. In this case a Tenax TA trap was connected to the UV-IMS as a pre-separation step in order to identify compounds present in the gasoline gaseous sample, such as benzene and toluene. Firstly, target analytes were trapped in a Tenax TA column at ambient temperature and then they were desorbed thermally in an oven and connected to the UV-IMS for their analysis. Instrumental parameters such as temperature ramp, sample gas flow rate, drift gas flow rate, adsorption time and adsorption flow rate were optimized to obtain high sensitivity, selectivity and precision to determine benzene and toluene in vapour gaseous samples. The UV-IMS was calibrated with standard gases generated in an exponential dilution flask, obtaining a limit of quantification of 1.8 and 1.9 mg m-3 for benzene and toluene, respectively. The method developed was successfully applied to identify these analytes in air samples close to a gasoline spillag

Physical Education in English. A proposal for working postural hygiene in Primary Education

In recent years, European Union has increased the demand for bilingual education as a tool to prepare young people in school and at work. This need has been reflected in the educational legislation of its member countries In Spain, since 2006 there is a basic competency related to foreign language learning. The Physical Education area has become an ideal means to facilitate the learning of English through play and movement. In order to facilitate the work of future teachers in the area, this article examines the teaching of Physical Education in the bilingual English. The current legislation that governs the implementation of bilingualism in schools will be presented, along with the most important methodological considerations for teaching our subject in English. Finally, in the section about practical applications, we present a circuit of activities to work postural hygiene in Primary Education. Each activity has its description in Spanish and English, along with the «teacher speech», with specific instructions to carry out in each of the exercise