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21.
Jim Braun Jon Dumm Francesco De Palma Chad Finley Albrecht Karle Teresa Montaruli 《Astroparticle Physics》2008,29(4):299-305
Neutrino telescopes are moving steadily toward the goal of detecting astrophysical neutrinos from the most powerful galactic and extragalactic sources. Here we describe analysis methods to search for high energy point-like neutrino sources using detectors deep in the ice or sea. We simulate an ideal cubic kilometer detector based on real world performance of existing detectors such as AMANDA, IceCube, and ANTARES. An unbinned likelihood ratio method is applied, making use of the point spread function and energy distribution of simulated neutrino signal events to separate them from the background of atmospheric neutrinos produced by cosmic ray showers. The unbinned point source analyses are shown to perform better than binned searches and, depending on the source spectral index, the use of energy information is shown to improve discovery potential by almost a factor of two. 相似文献
22.
The Upper Jurassic Tordillo Formation at Cañada Ancha area, northern Neuquén Basin, Argentina, comprises a multi-stage suit of predominantly alluvial sediments that is heterolithic in nature. In that suit, several lithofacies, architectural elements, and bounding surfaces of different order have been identified and their lateral and vertical distribution characterized. This analysis allowed the differentiation of 3 main units (lower, middle and upper), 20 subunits (C-1 to C-20), and the characterization of their alluvial styles.The lower unit (which comprises subunits C-1 to C-4) is mainly formed by fine- to medium-grained sandstones, which become medium- to coarse-grained towards the top. These sandstones characterize settings ranging from floodplains with isolated, unconfined flows, to more complex, vertically stacked, multi-storey sheet sandstones of braided fluvial systems. The middle unit (C-5 to C-10) is dominated by pale brown-grey fine-to coarse-grained sands and medium size subangular to angular conglomerates, which reflect amalgamated complexes of sandstone sheets and downstream accretion macroforms. Remarkably, this alluvial sedimentation was episodically punctuated by volcaniclastic flows. The upper unit (C-11 to C-20) consists of finer sediments, mainly pink to white fine-to medium grained sandstones and red to green siltstones. Towards the top, bioturbation becomes important, and also the presence of volcanosedimentary flows is noticeable. Fluvial settings include braided sheet sandstones with waning flood deposits evolving to isolated high-sinuosity fluvial systems, with flash flood deposits. At the top of this unit, facies may suggest marine influence.Vertical changes in the fluvial style result from both climatic and tectonic controls. A semiarid to arid climate and the active tectonism linked to the eastward migration of the Andean volcanic arc determined major bounding surfaces, fluvial style evolution and the presence of the volcano-sedimentary deposits. Different stages of high and low subsidence rates has been deduced from the vertical stacking of sediments. 相似文献
23.
A study of the mesoscale distribution of phytoplankton communities observed along the Portuguese upwelling coast in 1985–1986 made it possible to identify an assemblage composed by the coccolithophores Helicosphaera carteri, Syracosphaera pulchra and Coronosphaera mediterranea. The assemblage was consistently present in the coast in the following years (1991, 1992, 1994, 2003 and 2005) and from 1992 onwards, Rhabdosphaera clavigera was recognised as being part of it, although in low concentrations During late summer, this group of species showed higher affinities with upwelling waters of subtropical origin (ENACWst) on the SW coast. At the end of the upwelling season, in autumn, the assemblage was advected to the NW shelf due to the intensification of the poleward surface circulation or meridional seasonal changes of environmental conditions. The species maximum abundances were not coincident in space: H. carteri developed at the central part of the western coast while blooms of S. pulchra and C. mediterranea generally occurred further south, such as at the upwelling centre of cape S. Vicente. Syracosphaera pulchra blooms were characterised by lower concentrations of C. mediterranea and vice-versa. The above patterns were recurrent along the years but the relative abundance of each species appeared related to the interannual variability of physical conditions as the upwelling. 相似文献
24.
Christian Birkel Alicia Correa Barahona Clément Duvert Sebastián Granados Bolaños Andres Chavarría Palma Ana Maria Durán Quesada Ricardo Sánchez Murillo Harald Biester 《水文研究》2021,35(4):e14153
The impacts of forest conversion on runoff generation in the tropics have received much interest, but scientific progress is still hampered by challenging fieldwork conditions and limited knowledge about runoff mechanisms. Here, we assessed the runoff generation, flow paths and water source dynamics of a pristine rainforest catchment in Costa Rica using end member mixing analysis (EMMA) and a Bayesian mixing model (MixSIAR). Geochemical tracer data collected over a 4-week field campaign were combined with tritium data used to assess potential deeper groundwater flow pathways to the perennial stream. The streamflow composition was best captured using three end-members, namely throughfall, shallow (5–15 cm) and deeper (15–50 cm) soil water. We estimated the end-member contributions to the main stream and two tributaries using the two mixing approaches and found good agreement between results obtained from EMMA and MixSIAR. The system was overwhelmingly dominated by near-surface sources, with little evidence for deeper and older groundwater as tritium-derived baseflow mean transit time was between 2.0 and 4.4 years. The shallow soil flow pathway dominated streamflow contributions in the main stream (median 39% and 49% based on EMMA and MixSIAR, respectively), followed by the deeper soil (32% and 31%) and throughfall (25% and 19%). The two tributaries had even greater shallow soil water contributions relative to the main stream (83% and 74% for tributary A and 42% and 63% for tributary B). Tributary B had no detectable deep soil water contribution, reflecting the morphology of the hillslope (steeper slopes, shallower soils and lower vegetation density compared to hillslope A). Despite the short sampling campaign and associated uncertainties, this study allowed to thoroughly assess runoff generation mechanisms in a humid tropical catchment. Our results also provide a first comparison of two increasingly used mixing models and suggest that EMMA and MixSIAR yield comparable estimates of water source partitioning in this tropical, volcanic rainforest environment. 相似文献
25.
A study of the Calcidiscus genus in Lisbon Bay has revealed the presence of Calcidiscus quadriperforatus and Calcidiscus leptoporus. Samples were collected continuously on a weekly basis for four years (July 2001–May 2005) and on a cruise carried out in summer 2005, covering Lisbon Bay. Calcidiscus quadriperforatus and C. leptoporus developed in the same range of temperature and salinity, 11.5–21.5 °C and 26.9–36.3, respectively. The two species seemed to respond independently but had a co-occurring seasonal pattern nearshore, developing in different concentrations throughout the seasons. The maxima of both species occurred in low turbulent and nutrient enriched waters, which was also favourable for the development of larger coccospheres of C. quadriperforatus. The concentrations of both species decreased from 2001 until 2005, due to the intensification and persistence of upwelling and rainy periods.From late autumn until winter, mixed populations were observed nearshore, largely dominated by Calcidiscus quadriperforatus, in colder and nutrient enriched waters, while during spring, when temperatures begin to increase, only Calcidiscus leptoporus was observed, in mature upwelled waters. Calcidiscus quadriperforatus was considered more opportunistic than C. leptoporus. The availability of nutrients seemed to have influenced the size increase of C. quadriperforatus coccospheres. Both species developed offshore during summer, when the shelf is occupied by colder turbulent upwelled waters. A short downwelling episode in summer 2005, associated with two counter-rotating mesoscale eddies, responsible for a strong north-eastward flow of warm oceanic waters into the bay, allowed the development of C. quadriperforatus nearshore. Contemporary satellite images revealed the presence and onshore displacement of these waters and C. quadriperforatus and C. leptoporus distribution highlighted these conditions. The development of each species nearshore also gave indications of local oceanographic changes during winter and spring. 相似文献
26.
Márjore Antunes Maísa Trevisan Antunes Andreia Neves Fernandes Janaina da Silva Crespo Marcelo Giovanela 《Environmental Earth Sciences》2013,69(3):959-968
The nutrients, carbon, nitrogen and phosphorus, significantly affect the quality of aquatic environments, especially when present at concentrations above natural levels. In this context, the sedimentary column can act as an environment for storage or accumulation of these nutrients and for the reprocessing of such substances in the water column and aquatic biota. In this context, this study aimed to estimate the concentration of total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP), inorganic phosphorus (IP) and organic phosphorus (OP) in seven sediment samples that were collected from the Marrecas Stream microbasin (Caxias do Sul, Rio Grande do Sul State, Brazil). The relationships among the sediment nutrient concentrations and the levels of organic matter (OM), fine material (silt–clay) and the concentration of the metal species, Al, Fe and Mn, as well as the possible nutrient sources to the stream studied were also evaluated. The data set suggest that the TOC and IP appear to have a direct correlation with the vast riparian vegetation present in areas adjacent to the sampling points and to the physico-chemical properties of the water and sedimentary column. Moreover, the results obtained for TN suggest that its concentration possibly suffers interference from the temperature of the water and its oxygenation, in addition to other biological activities. On the other hand, one cannot rule out human interference, mainly in the levels of OP, possibly due to the inflow of domestic sewage to the stream. 相似文献
27.
Although there are multiple methods for modeling matrix covariance functions and matrix variograms in the geostatistical literature, the linear coregionalization model is still widely used. In particular it is easy to check to ensure whether the matrix covariance function is positive definite or that the matrix variogram is conditionally negative definite. One of the difficulties in using a linear coregionalization model is in determining the number of basic structures and the corresponding covariance functions or variograms. In this paper, a new procedure is given for identifying the basic structures of the space–time linear coregionalization model and modeling the matrix variogram. This procedure is based on the near simultaneous diagonalization of the sample matrix variograms computed for a set of spatiotemporal lags. A case study using a multivariate spatiotemporal data set provided by the Environmental Protection Agency of Lombardy, Italy, illustrates how nearly simultaneous diagonalization of the empirical matrix variograms simplifies modeling of the matrix variograms. The new methodology is compared with a previous one by analyzing various indices and statistics. 相似文献
28.
The Italian strong motion network 总被引：2，自引：2，他引：0
Antonella Gorini Mario Nicoletti Paolo Marsan Riccardo Bianconi Rita De Nardis Luisa Filippi Sandro Marcucci Franco Palma Elisa Zambonelli 《Bulletin of Earthquake Engineering》2010,8(5):1075-1090
The Italian Strong Motion Network is a permanent monitoring system run by the Italian national emergency management department
(Dipartimento della Protezione Civile, DPC). The network is known as RAN (Rete Accelerometrica Nazionale). An extensive project
for updating and improving the technology of RAN instruments as well as the number of recording points was performed in the
last 10 years. A wide site selection survey was carried out from eastern Sicily along the Italian peninsula, covering high
seismic risk areas. The recording station density and the choice of high-quality digital strong motion instruments ensure
reliability of the RAN network in the long-term. At the end of 2008, the free field sites selection and instruments installation,
planned in the project, were quite completed. In planning and drawing the new RAN, special attention has been devoted to the
robustness of the transmission systems, and to the distribution of new stations in order to ensure plenty of data during a
seismic emergency. We spent special care both in the estimation of the RAN site responses and in the diffusion of the strong
motion data. In order to better identify damaged earthquake areas, improved ground motion parameters need to be set. Such
parameters will also assist future progress for engineering seismic design techniques as well as disaster mitigation. 相似文献
29.
Ricardo M. Palma Diego A. Kietzmann Susana Adamonis Jos Lpez Gmez 《Sedimentary Geology》2009,221(1-4):127-140
The Neuquén back-arc basin is located on the west margin of the South American platform between latitudes 36° and 40° S. The basin is famous for its continuous sedimentary record from the Late Triassic to Cenozoic comprising continental and marine clastic, carbonate, and evaporitic deposits up to 2.600 m in thickness.The stratigraphical and paleontological studies of the outcrops of the La Manga Formation, Argentina, located near the Bardas Blancas region, Mendoza province (35° S and 69° O) allow the reconstruction of the sedimentary environments of an Oxfordian carbonate ramp, where outer ramp, middle ramp, inner ramp (oolitic shoal), inner ramp margin (patch reef) lagoon and paleokarst were differentiated. The reefs consist of back reef facies and in situ framework of coral boundstones that was formed at the top of shallowing-upward succession.Coral reefs were analyzed by defining coral colonies shapes, paleontological content, coral diversity and taphonomy studies. In some studied sections abundant fragments of gryphaeids, encrusting bryozoans, and isolated sponges provided a suitable substrate for coral colonization; however, other sections show an increase in the proportions of ooids, peloidal and coral intraclasts.The core reef facies is composed of white-grey unstratified and low diversity scleractinian coral limestone dominated by robust and thinly branching corals with cerioid–phocoid growths and massive coral colonies with meandroid–thamnasteroid growth forms.The assemblage is characterized by Actinastraea sp., Australoseris sp., Thamnasteria sp. and Garateastrea sp. Internal facies organization and different types of coral colonies allow to recognize the development of varying framework as well as intercolony areas. A superstratal growth fabric characterizes the coral assemblage. On the basis of coral growth fabric (branche and domal types), the reef of La Manga Formation is considered a typical mixstones. The intercolony areas consist of biomicrites and biomicrorudites containing abundant coral fragments, parautochthonous gryphaeids and another bivalves (Ctenostreon sp.), gastropods (Harpagodes sp., Natica sp.), echinoderms test and spines (Plegiocidaris sp.), miliolids, Cayeuxia sp., Acicularia sp., Salpingoporella sp., intraclasts, ooids, peloids and coated grains.The domal growth forms are probably more protected against biological and physical destruction, meanwhile delicate branching growth forms with very open and fragile framework were more affected and fragmented due to wave action and bioerosion.The reef fabric shows different intervals of truncation as consequence of erosion resulting from coral destruction by storm waves or currents. The maximum flooding surface separates oolitic shoal facies below from the aggradational and progradational coralline limestones facies above. Subsequent sea-level fall and karstification (148 Ma) affected reef and oolitic facies. 相似文献
30.
C. de Leon-Condes C. Barrera-Díaz J. Barrios E. Becerril H. Reyes-Pérez 《International Journal of Environmental Science and Technology》2017,14(4):707-716
Organic emerging micropollutants are persistent during the biological process used in treatment plants and have the tendency to accumulate in the sludge. Since a common method of final sludge disposal is the land application, there are potential risks associated with the presence of contaminants within the sludge. In this work, the removal efficiency of endocrine-disrupting chemicals, namely bisphenol A, nonylphenol and triclosan from sludge was investigated using ozonation and electrooxidation using boron-doped diamond electrodes. Both procedures were studied to determine the optimal conditions (pH, current density and ozone flow) for removing these chemicals in an hour. With the obtained conditions, a coupled system ozonation–electrooxidation was used with the goal to have better pollutant elimination. Results indicate that these compounds could be effectively removed by the coupled system; the diminutions were Bisphenol A 86%, nonylphenol 68% and triclosan 67%. Also improvements in the quality of aqueous phase were obtained, and for instance, the chemical oxygen demand, color and turbidity, were abated in 62, 61 and 66%, respectively. Moreover, an additional advantage of the coupled system is the absence of any secondary pollution. 相似文献