889 research outputs found

    Strong-mixing induced deep ocean heat uptake events in the North Atlantic.

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    The deceleration of the upper ocean heat storage during the last decade has resulted in an active search for the ’missing heat’ in the deep ocean. Modeling work has provided new insights into the role of the central Pacific Ocean on the present hiatus in global warming and the efficient transfer of heat to the deep ocean, but recent studies have highlighted also the large contribution of the North Atlantic basin to these processes, mainly based on ocean observations. The deep ocean heat uptake (below 300 m) in the North Atlantic is not confined to the subpolar gyre region but extends to mid-latitudes of the Eastern North Atlantic (ENA), requiring an additional process for its explanation other than deep convection considered until now. Here, using oceanographic in-situ data, we describe a mechanism of heat and salt injection to the deep ocean after years of warming and saltening at the surface occurred both in regions of mode (43º-48ºN) and deep water (74º-76ºN) formation in the ENA. The mechanism, although punctual meditated by strong winter mixing events, is between 2 and 6 times higher than the 2000-2010 ocean heat uptake at depths of mode (300-700m) and deep water (>2000m) formation, contributing significantly to the observed deep ocean heat uptake in the North Atlantic. Nutrient, hydrographic and reanalysis data indicate that the strong mixing-induced deep ocean heat uptake events at areas of mode and deep water formation in the North Atlantic are connected through the northward propagation of salty ENA mode waters triggered by the contraction of the subpolar gyre reinforced by the occurrences of blocking anomalies in the ENA. Such connection is not unique of the last decade but observed also during the 1960s. Natural climate variability seems the ultimate driver of the strong mixing-induced deep ocean heat uptake events, although the anthropogenic global warming and its forcing on the Arctic sea-ice retreat and frequency of extreme weather events could modify their effects.0,000

    Macrofaunal communities in the Gioia Canyon (Southern Tyrrhenian Sea, Italy)

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    Submarine canyons play pivotal roles in the physical, biological and ecological processes of coastal areas, especially in closed or semi-closed basins as the Mediterranean Sea, influencing the biodiversity and the abundance of the benthic fauna. On February 2013, during the Tyrrhenian Gravity Flows (TyGraF) campaign, samples have been collected along the Gioia Canyon Basin (Italy) with the aim to describe the taxonomical composition and the abundances of the macrobenthic assemblages, filling the gap of knowledge in this area. A total of 93 taxa were identified, and the Annelida was the phylum with the highest number of specimens and most diversified (46 taxa). The polychaetes Sternaspis scutata, Prionospio cirrifera and Monticellina sp., the bivalves Thyasira sp.1 and Saccella commutata and the amphipods belonging to the genera Ampelisca and Harpinia showed the highest densities in the studied area; however, results suggest low values of the abundances of the macrobenthos if compared with those generally reported for other canyons, both inside and outside the Mediterranean Sea. The marine biotic index (AMBI) highlights that the canyon system and the surrounded area were slightly disturbed and characterized by a high percentage of tolerant taxa. This study is the first baseline for future analyses of the macrobenthic communities of this area

    New data on opisthobranchs (Mollusca: Gastropoda) from the southwestern coast of Portugal

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    The present papers reports the results obtained from different field samplings carried out on the southwestern Portuguese coast during July 2002, within the scope of three research projects on opisthobranch molluscs. Two areas were sampled, one around Sagres (37° 00' N, 8° 57' W) on the SW tip of the Portuguese mainland, the other near Sines (37° 57' N, 8° 53' W), 110 km north of the other site. Eighty-one species of opisthobranchs were identified, six of them new to the Portuguese fauna.Se exponen los resultados obtenidos a partir de los diferentes muestreos realizados en julio de 2002 en el suroeste de la costa portuguesa, en el ámbito de tres proyectos centrados en los moluscos opistobranquios. Se muestrearon dos áreas: una en los alrededores de Sagres (37° 00' N, 8° 57' O), en el extremo suroeste continental de Portugal y la otra en los alrededores de Sines (37° 57' N, 8° 53' O), a 110 km al norte de la primera. Se identificaron 81 especies de opistobranquios, seis de las cuales constituyen nuevas citas para la fauna portuguesa.Instituto Español de Oceanografí

    Patient organ and effective dose estimation in CT: comparison of four software applications

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    Background: Radiation dose in computed tomography (CT) has become a topic of high interest due to the increasing numbers of CT examinations performed worldwide. Hence, dose tracking and organ dose calculation software are increasingly used. We evaluated the organ dose variability associated with the use of different software applications or calculation methods. Methods: We tested four commercial software applications on CT protocols actually in use in our hospital: CT-Expo, NCICT, NCICTX, and Virtual Dose. We compared dose coefficients, estimated organ doses and effective doses obtained by the four software applications by varying exposure parameters. Our results were also compared with estimates reported by the software authors. Results: All four software applications showed dependence on tube voltage and volume CT dose index, while only CT-Expo was also dependent on other exposure parameters, in particular scanner model and pitch caused a variability till 50%. We found a disagreement between our results and those reported by the software authors (up to 600%), mainly due to a different extent of examined body regions. The relative range of the comparison of the four software applications was within 35% for most organs inside the scan region, but increased over the 100% for organs partially irradiated and outside the scan region. For effective doses, this variability was less evident (ranging from 9 to 36%). Conclusions: The two main sources of organ dose variability were the software application used and the scan region set. Dose estimate must be related to the process used for its calculation
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