Anundance of phytoplankton at time series station DYNAPROC

A general study of biogeochemical processes (DYNAPROC cruise) was conducted in May 1995 at a time-series station in the open northwestern Mediterranean Sea where horizontal advection was weak. Short-term variations of the vertical distributions of pico- and nanophytoplankton were investigated over four 36-h cycles, along with parallel determinations of metabolic CO2 production rates and amino acid-containing colloid (AACC) concentrations at the chlorophyll maximum depth. The vertical (0-1000-m depth) distributions of (i) AACC, (ii) suspended particles and (iii) metabolic CO2 production rate were documented during the initial and final stages of these 36-h cycles. This study was concerned with diel vertical migration (DVM) of zooplankton, which provided periodic perturbations. Accordingly, the time scale of the experimental work varied from a few hours to a few days. Although all distributions exhibited a periodic behaviour, AACC distributions were generally not linked to diel vertical migrations. In the subsurface layer, Synechococcus made the most abundant population and large variations in concentration were observed both at day and at night. The corresponding integrated (over the upper 90 m) losses of Synechococcus during one night pointed to a potential source of exported organic matter amounting to 534 mg C/m**2. This study stresses the potential importance of organic matter export from the euphotic zone through the daily grazing activity of vertically migrating organisms, which would not be accounted for by measurements at longer time scales. The metabolic CO2 production exhibited a peak of activity below 500 m that was shifted downward, apparently in a recurrent way and independently of the vertical distributions of AACC or of suspended particulate material. To account for this phenomenon, a 'sustained wave train» hypothesis is proposed that combines the effect of the diel superficial faecal pellet production by swarming migrators and the repackaging activity of the nonmigrating midwater populations. Our results confirm the recent finding that the particulate compartment is not the major source of the observed instantaneous remineralisation rate and shed a new light on the fate of organic matter in the aphotic zone.

Mineral composition and experimental results from XRD analyses of sediments from ODP Leg 190 sites

X-ray diffraction analyses of the clay-sized fraction of sediments from the Nankai Trough and Shikoku Basin (Sites 1173, 1174, and 1177 of the Ocean Drilling Program) reveal spatial and temporal trends in clay minerals and diagenesis. More detrital smectite was transported into the Shikoku Basin during the early-middle Miocene than what we observe today, and smectite input decreased progressively through the late Miocene and Pliocene. Volcanic ash has been altered to dioctahedral smectite in the upper Shikoku Basin facies at Site 1173; the ash alteration front shifts upsection to the outer trench-wedge facies at Site 1174. At greater depths (lower Shikoku Basin facies), smectite alters to illite/smectite mixed-layer clay, but reaction progress is incomplete. Using ambient geothermal conditions, a kinetic model overpredicts the amount of illite in illite/smectite clays by 15%-20% at Site 1174. Numerical simulations come closer to observations if the concentration of potassium in pore water is reduced or the time of burial is shortened. Model results match X-ray diffraction results fairly well at Site 1173. The geothermal gradient at Site 1177 is substantially lower than at Sites 1173 and 1174; consequently, volcanic ash alters to smectite in lower Shikoku Basin deposits but smectite-illite diagenesis has not started. The absolute abundance of smectite in mudstones from Site 1177 is sufficient (30-60 wt%) to influence the strata's shear strength and hydrogeology as they subduct along the Ashizuri Transect.

Nicotinamide nucleotide and adenylate concentrations in mante, siphon and gill tissue of old and young Laternula elliptica individuals under control and experimental conditions

Future oceans are predicted to contain less oxygen than at present. This is because oxygen is less soluble in warmer water and predicted stratification will reduce mixing. Hypoxia in marine environments is thus likely to become more widespread in marine environments and understanding species-responses is important to predicting future impacts on biodiversity. This study used a tractable model, the Antarctic clam, Laternula elliptica, which can live for 36 years, and has a well-characterized ecology and physiology to understand responses to hypoxia and how the effect varied with age. Younger animals had a higher condition index, higher adenylate energy charge and transcriptional profiling indicated that they were physically active in their response to hypoxia, whereas older animals were more sedentary, with higher levels of oxidative damage and apoptosis in the gills. These effects could be attributed, in part, to age-related tissue scaling; older animals had proportionally less contractile muscle mass and smaller gills and foot compared with younger animals, with consequential effects on the whole-animal physiological response. The data here emphasize the importance of including age effects, as large mature individuals appear to be less able to resist hypoxic conditions and this is the size range that is the major contributor to future generations. Thus, the increased prevalence of hypoxia in future oceans may have marked effects on benthic organisms' abilities to persist and this is especially so for long-lived species when predicting responses to environmental perturbation.

Experimental investigation of radio signal propagation in scientific facilities for telerobotic applications

Understanding the radio signal transmission characteristics in the environment where the telerobotic application is sought is a key part of achieving a reliable wireless communication link between a telerobot and a control station. In this paper, wireless communication requirements and a case study of a typical telerobotic application in an underground facility at CERN are presented. Then, the theoretical and experimental characteristics of radio propagation are investigated with respect to time, distance, location and surrounding objects. Based on analysis of the experimental findings, we show how a commercial wireless system, such as Wi-Fi, can be made suitable for a case study application at CERN.

Estudio experimental del centelleo troposférico en presencia de precipitación

Este Proyecto Fin de Grado tiene como objetivo realizar un estudio del centelleo troposférico en presencia de lluvia en la banda Ka. Para ello se han utilizado los datos obtenidos de un enlace Tierra-satélite mediante una estación receptora situada en la ETSIT UPM. En la primera parte de este proyecto, se ha realizado un estudio teórico, no demasiado profundo de los principales fenómenos que afectan a este tipo de enlaces, comentando algunos modelos de predicción y profundizando en el centelleo troposférico, ya que es el principal tema que se trata en este proyecto. En segundo lugar, se ha realizado el experimento. En la primera parte se ha comprobado que efectivamente se cumple el modelo de pendiente de -20 dB/dec debidos a la lluvia, todo ello procesando los datos que han sido tomados en la ETSIT mediante Matlab. En la segunda parte, se han tratado individualmente distintos tipos de eventos con el fin de determinar una frecuencia de corte adecuada para realizar la separación mediante filtrado de las componentes de lluvia respecto a las de centelleo, así como verificar el cumplimiento de la pendiente en el espectro de -26 dB/dec debida al centelleo. Posteriormente, una vez que se ha obtenido una frecuencia de corte adecuada para el filtro, he separado las componentes espectrales debidas al centelleo de las componentes debidas a la lluvia. Se ha obtenido la varianza de una serie de eventos, ya que es el parámetro que mejor caracteriza la intensidad del centelleo y la hemos comparado en los diferentes meses para observar su variación, ya que las lluvias de verano tienen asociadas la presencia de turbulencias mayores respecto a las de invierno. Para finalizar el proyecto, se han expuesto las conclusiones a las que hemos llegado mediante el mismo, comentando también las posibles líneas de investigación futuras. ABSTRACT. The aim of this Project is to make a study about tropospheric Scintillation in presence of rain in the Ka band. For this purpose, the data obtained in an Earth-satellite link by a receiving station located at ETSIT UPM will be used. In the first part of this project, a non-detailed theoretical study of the principal phenomena affecting this type of links has been performed, commenting some prediction models and deepening in tropospheric Scintillation, because this is the principal objective of this project. In the second part, the experiment has been completed. In the first part the fulfillment of -20 dB/dec of slope due to the rain has been proved, after processing the data obtained in the ETSIT using Matlab. In the second part different types of events have been treated in order to determine an adequate cut frequency with the purpose of separating by filtering the components of the rain from the components of scintillation as well as verifying the fulfillment of the slope in the spectrum of -26 dB/dec due to scintillation. Afterwards, once that one suitable cut frequency for the filter has been obtained, the components of scintillation respect to the components produced by rain have been separated. The variance of a series of events has been obtained, because it is the parameter that best characterizes the scintillation intensity and during the different months it has been compared with the objective of observing its variation, due to the higher association of summer rains to the presence of greater turbulences than during winter rains. To complete this project I have presented the final conclusions to which we have come, also commenting on the possible future lines of investigation.