Creación de experiencias virtuales en física nuclear

El estudio de la radiactividad y su influencia en los seres vivos es un tema fundamental para la formación de los alumnos de los grados en Biología y Ciencias del Mar, y por lo tanto aparece incluido en el plan de estudios de la asignatura de Física de las dos carreras anteriormente mencionadas. A pesar de esto, dicha signatura no cuenta con ninguna práctica de laboratorio en el tema de radiactividad. Esto es debido, principalmente, al alto coste de los equipos y a cuestiones de seguridad. Con el objetivo de solventar este problema en la formación de los alumnos de Física hemos programado, usando el lenguaje JAVA, dos prácticas de laboratorio virtuales en el área de radiactividad. En una de las experiencias, el alumno mide la evolución de la actividad de una muestra radiactiva con el tiempo y a partir de esto podrá obtener la vida media del isótopo radiactivo estudiado, calcular la cantidad de isótopo que queda en la muestra al transcurrir un cierto tiempo, o evaluar el tiempo necesario que debe de transcurrir para que quede un cierto porcentaje del material radiactivo inicial. En la otra experiencia la medición de la actividad y la masa de una muestra dada de carbono de origen biológico, permitirá establecer la edad de la muestra usando el método del 14C. En ambas prácticas el alumno utiliza el instrumental virtual tal y como si estuviera en un laboratorio real con el instrumental adecuado. La interactividad de la práctica y la posibilidad de realizarla fuera de la universidad, a través de internet, hacen de los experimentos virtuales diseñados un excelente complemento a las prácticas tradicionales de laboratorio.

Auto-atribuciones académicas: diferencias de género y curso en estudiantes de educación secundaria

El análisis de las autoatribuciones académicas constituye un aspecto esencial del componente afectivo y emocional de la motivación escolar en estudiantes de educación secundaria obligatoria (ESO). El objetivo de este estudio fue analizar, mediante un diseño transversal, las diferencias de género y curso y el papel predictivo de estas variables en las atribuciones causales académicas de los alumnos medidas a través de las escalas generales de la Sydney Attribution Scale (SAS). El cuestionario fue administrado a 2.022 estudiantes (51.08% chicos) de 1º a 4º de ESO. El rango de edad fue de 12 a 16 años (M = 13.81; DT = 1.35). Los resultados derivados de los análisis de varianza y de los tamaños del efecto (índice d) revelaron que los chicos atribuyeron sus éxitos significativamente más a su capacidad, mientras las chicas los atribuyeron significativamente más al esfuerzo. Respecto a las atribuciones de fracaso escolar, los resultados indicaron que los chicos los atribuyeron significativamente más a la falta de esfuerzo que las chicas. Asimismo, se hallaron diferencias de curso académico en la mayoría de las atribuciones causales analizadas. Los análisis de regresión logística indicaron que el género y el curso fueron predictores significativos de las atribuciones causales académicas, aunque los resultados variaron para cada una de las escalas de la SAS. Los resultados son discutidos en relación a la necesidad de diseñar programas de intervención que tengan en cuenta las variables sexo y curso académico.

(Table 1) Petrological description and consolidation properties of ODP Site 186-1150 and Hole 186-1151A

In order to determine the shear parameters of the forearc sedimentary strata drilled during Ocean Drilling Program Leg 186, West Pacific Seismic Network, Japan Trench, eight whole-round samples were selected from different depths in the drilled sections of Sites 1150 and 1151. Whereas Site 1150 lays above the seismically active part of the subduction zone, Site 1151 is situated in an aseismic zone. The aim of the triaxial tests was, apart from determination of the static stress strain behavior of the sediments, to test the hypothesis that the static stress strain parameter could differ for each sites. In order to simulate undrained deformation conditions according to the high clay mineral content of the strata, consolidated undrained shear tests were performed in a triaxial testing setup. Measurements of water content, grain density, organic content, and microtextural investigations under the scanning electron microscope (SEM) accompanied the compression experiments. After the saturation and consolidation stages were completed, failure occurred in the compression stage of the experiments at peak strengths of 280-7278 kPa. The stiffness moduli calculated for each sample from differential stress vs. strain curves show a linear relationship with depth and range between 181 and 5827 kPa. Under the SEM, the artificial fault planes of the tested specimen only show partial alignment of clay minerals because of the high content of microfossils.

Diatom abundance in sediments of ODP Holes 186-1150A and 186-1151C

The diatom flora from two sediment cores recovered from the upper 27 meters below seafloor (mbsf) in the oceanic frontal area off Sanriku, northeast Japan, during Ocean Drilling Program Leg 186 were analyzed. Diatom abundance seems to be in interglacial stages and suggests a south-north shifting of the frontal area. Diatom temperature values are less reliable because frequency of the warm-water species is smaller. Site 1151 was in a warm climate at ~50 ka, as were Deep Sea Drilling Project Sites 579 and 580 in the western North Pacific Ocean. A mixed diatom assemblage in the upper 3 mbsf at Site 1150 is evidence that the Tsugaru Warm Current flowed into the studied area through the Tsugaru Strait.

Data compilation of ESOP

The work in this sub-project of ESOP focuses on the advective and convective transforma-tion of water masses in the Greenland Sea and its neighbouring areas. It includes observational work on the sub-mesoscale and analysis of hydrographic data up to the gyre-scale. Observations of active convective plumes were made with a towed chain equipped with up to 80 CTD sensors, giving a horizontal and vertical resolution of the hydrographic fields of a few metres. The observed scales of the penetrative convective plumes compare well with those given by theory. On the mesoscale the structure of homogeneous eddies formed as a result of deep convection was observed and the associated mixing and renewal of the intermediate layers quantified. The relative importance and efficiency of thermal and haline penetrative convection in relation to the surface boundary conditions (heat and salt fluxes and ice cover) and the ambient stratification are studied using the multi year time series of hydro-graphic data in the central Greenland Sea. The modification of the water column of the Greenland Sea gyre through advection from and mixing with water at its rim is assessed on longer time scales. The relative contributions are quantified using modern water mass analysis methods based on inverse techniques. Likewise the convective renewal and the spreading of the Arctic Intermediate Water from its formation area is quantified. The aim is to budget the heat and salt content of the water column, in particular of the low salinity surface layer, and to relate its seasonal and interannual variability to the lateral fluxes and the fluxes at the air-sea-ice interface. This will allow to estimate residence times for the different layers of the Greenland Sea gyre, a quantity important for the description of the Polar Ocean carbon cycle.

Combined effects of coral reef foraminifera Marginopora vertebralis and Heterostegina depressa in a multi-fractorial experiment

Warming and changes in ocean carbonate chemistry alter marine coastal ecosystems at an accelerating pace. The interaction between these stressors has been the subject of recent studies on reef organisms such as corals, bryozoa, molluscs, and crustose coralline algae. Here we investigated the combined effects of elevated sea surface temperatures and pCO2 on two species of photosymbiont-bearing coral reef Foraminifera: Heterostegina depressa (hosting diatoms) and Marginopora vertebralis (hosting dinoflagellates). The effects of single and combined stressors were studied by monitoring survivorship, growth, and physiological parameters, such as respiration, photochemistry (pulse amplitude modulation fluorometry and oxygen production), and chl a content. Specimens were exposed in flow-through aquaria for up to seven weeks to combinations of two pCO2 (~790 and ~490 µatm) and two temperature (28 and 31 °C) regimes. Elevated temperature had negative effects on the physiology of both species. Elevated pCO2 had negative effects on growth and apparent photosynthetic rate in H.depressa but a positive effect on effective quantum yield. With increasing pCO2, chl a content decreased in H. depressa and increased in M. vertebralis. The strongest stress responses were observed when the two stressors acted in combination. An interaction term was statistically significant in half of the measured parameters. Further exploration revealed that 75 % of these cases showed a synergistic (= larger than additive) interaction between the two stressors. These results indicate that negative physiological effects on photosymbiont-bearing coral reef Foraminifera are likely to be stronger under simultaneous acidification and temperature rise than what would be expected from the effect of each of the stressors individually.

Le prince Igor; opéra en quatre actes, avec prologue.

Russian title at head of t.-p.

High-intensity noise and military operations: An evaluation

"Project NR 140-069. Contract NONR-1151 (01)."