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51.
Cloud condensation nuclei from biomass burning during the Amazonian dry-to-wet transition season 总被引:1,自引:0,他引:1
Jorge Alberto Martins Fábio Luiz T. Gonçalves Carlos A. Morales Gilberto F. Fisch Francisco Geraldo M. Pinheiro João Bosco V. Leal Júnior Carlos J. Oliveira Emerson M. Silva José Carlos P. Oliveira Alexandre A. Costa Maria Assunção F. Silva Dias 《Meteorology and Atmospheric Physics》2009,104(1-2):83-93
Aircraft measurements of cloud condensation nuclei (CCN) during the Large-Scale Biosphere–Atmosphere Experiment in Amazonia (LBA) were conducted over the Southwestern Amazon region in September–October 2002, to emphasize the dry-to-wet transition season. The CCN concentrations were measured for values within the range 0.1–1.0% of supersaturation. The CCN concentration inside the boundary layer revealed a general decreasing trend during the transition from the end of the dry season to the onset of the wet season. Clean and polluted areas showed large differences. The differences were not so strong at high levels in the troposphere and there was evidence supporting the semi-direct aerosol effect in suppressing convection through the evaporation of clouds by aerosol absorption. The measurements also showed a diurnal cycle following biomass burning activity. Although biomass burning was the most important source of CCN, it was seen as a source of relatively efficient CCN, since the increase was significant only at high supersaturations. 相似文献
52.
In this paper we present a hydrologic application of a new statistical learning methodology called support vector machines (SVMs). SVMs are based on minimization of a bound on the generalized error (risk) model, rather than just the mean square error over a training set. Due to Mercer's conditions on the kernels, the corresponding optimization problems are convex and hence have no local minima. In this paper, SVMs are illustratively used to reproduce the behavior of Monte Carlo-based flow and transport models that are in turn used in the design of a ground water contamination detection monitoring system. The traditional approach, which is based on solving transient transport equations for each new configuration of a conductivity field, is too time consuming in practical applications. Thus, there is a need to capture the behavior of the transport phenomenon in random media in a relatively simple manner. The objective of the exercise is to maximize the probability of detecting contaminants that exceed some regulatory standard before they reach a compliance boundary, while minimizing cost (i.e., number of monitoring wells). Application of the method at a generic site showed a rather promising performance, which leads us to believe that SVMs could be successfully employed in other areas of hydrology. The SVM was trained using 510 monitoring configuration samples generated from 200 Monte Carlo flow and transport realizations. The best configurations of well networks selected by the SVM were identical with the ones obtained from the physical model, but the reliabilities provided by the respective networks differ slightly. 相似文献
53.
Yara Schaeffer-Novelli Hilda de Souza Lima Mesquita Gilberto Cintrón-Molero 《Estuaries and Coasts》1990,13(2):193-203
The Cananéia Lagoon estuarine system lies at 25°S, near the latitudinal limit for mangroves. It is 110 km long, consisting of 1–3 km wide channels behind a barrier island, with narrow inlets at the southern and northern ends. Average and maximum depths are 6 m and 12 m. The system is microtidal and subtropical. Mean annual temperature is 21.4°C (annual amplitude=7.0°C). When the area receives sporadic frosts, temperatures close to 2°C occur in the estuary. Annual precipitation (2,270 mm) exceeds annual potential evapotranspiration (1,656 mm). The water budget of the 1,339 km2 watershed is controlled primarily by local rainfall. Before 1978, a large river discharged a significant portion of its flow into the lagoon, but closure of the diversionary channel has since caused changes in salinity, phytoplankton populations, and mangrove coverage. About 90 km2 of intertidal habitat is occupied by mangroves and tidal marsh; mangroves are dominant. Fringe and riverine forests (dominated byRhizophora) are more structurally developed than the basins dominated byLaguncularia and have higher litterfall rates (2.08 g m?2 d?1, fringes; 1.04 g m?2d?1, basins). Primary production exhibits pronounced seasonal pulses; heterotrophic processes lag photosynthetic production and are partially driven by particulate matter inputs. Synthetic models must consider the spatial and temporal heterogeneity of this region. 相似文献
54.
Quantifying the reefscape transformation of a coastal Caribbean coral reef during a phase shift and the associated coastal landscape change 下载免费PDF全文
Abigail Martínez‐ Rendis Gilberto Acosta González José Luis Hernández‐Stefanoni Jesús Ernesto Arias González 《Marine Ecology》2016,37(3):697-710
Caribbean coral reefs are under strong natural and human pressures and many have undergone phase shifts as a result of local and global change. However few studies have quantified the extent of these phase shifts and the potential impacts that they have on coral reef communities. A temporal comparative analysis of several coral reefscape and landscape metrics was conducted for data from Mahahual, Quintana Roo, Mexico, between the years 2000 and 2006, when a phase shift occurred. Landscape metrics were calculated from coral reef and coastal cover maps obtained by multispectral satellite image classification using IKONOS satellite imagery. These metrics showed that the coastal landscape and reefscape of Mahahual lost 85 ha of vegetation cover and 43 ha of coral cover over 6 years, respectively. Coastal landscape transformation was induced by the construction of a cruise ship pier and multiple associated tourist developments along the coast, such as hotels and restaurants, meanwhile alteration of the reefscape may be associated with potential stressors such as coastal development, bleaching events and hurricanes. 相似文献
55.
Ogbaghebriel Berakhi L. Brancaccio G. Calderoni M. Coltorti F. Dramis Mohammed M. Umer 《Geomorphology》1998,23(2-4)
This paper presents a geomorphologic–stratigraphic analysis of a travertine dammed lacustrine–swampy sedimentary sequence, composed of clay, peaty layers and phytoclastic travertine sands, deeply incised by the Mai Maikden river, on the Highlands of Tigray (Northern Ethiopia). Radiocarbon datings of peaty deposits allow us to establish that the travertine dams have developed at least between 7310±90 yr B.P. and 5160±80 yr B.P. In the upper part of the sequence, palaeochannels filled with travertine and limestone coarse gravels and blocks, indicate the activation of concentrated erosion on the surrounding slopes. Later, both the travertine dam and the lacustrine–swampy deposits were buried by alluvial and colluvial sediments, still mixed with large amounts of organic matter, testifying to generalized slope erosion processes. The end of travertine deposition may be connected with a progressive reduction of vegetation cover and the subsequent decrease of CO2 in groundwater. The occurrence of the latter phenomena may be related to the onset of drier climatic conditions even though the finding of a large prehistoric settlement in the area, also indicates some influence of human impact. 相似文献
56.
Granulite rocks are exposed in eastern Minas Gerais, Brazil. Its early neoproterozoic evolution is characterised by a history of an active continental margin, including the accretion of suspect terranes. The Manhuaçu Terrane is one of those which is represented by a granitic continental plutonic arc and terrigeneous metasediments reflecting a continental margin. A metasedimentary gneiss belt at this margin with shallow to deep marine clastic lithologies as well as metavolcanic and metaplutonic mafic rocks was interpreted as an extensive tectonic segment with suspect development in a back-arc setting. Fragments of a volcanic arc are identified and interpreted as an evidence for a probable island-arc domain. The granulites occur as massive rocks as well as high-grade gneisses and show lithological, structural and metamorphic attributes consistent with their host belt type. In the western portion granulites derived from sedimentary protoliths, have been deposited, deformed and metamorphosed together with the mafic intrusions and as well as with their crystallization. Regional uplift exposed these rocks probably immediately after the metamorphism. In these belts the metamorphic grade is not uniform, especially where uplifting has exposed oblique cross sections over the granulitic rocks. Geothermobarometric calculations indicate that the granulites has been generated under T conditions between 800 and 990 ± 50 C and from medium (4.8 kb) to relatively high (10.0 kb) pressures. 相似文献
57.
Cattari Serena Calderoni Bruno Cali Ivo Camata Guido de Miranda Stefano Magenes Guido Milani Gabriele Saetta Anna 《Bulletin of Earthquake Engineering》2022,20(4):1939-1997
Bulletin of Earthquake Engineering - This paper provides a comphrensive review of the critical aspects of nonlinear modeling for evaluating the seismic response of masonry structures, emphasizing... 相似文献
58.
Antonella Longo Paolo Papale Melissa Vassalli Gilberto Saccorotti Chiara P. Montagna Andrea Cassioli Salvatore Giudice Enzo Boschi 《Bulletin of Volcanology》2012,74(4):873-880
Many volcanic eruptions are shortly preceded by injection of new magma into a pre-existing, shallow (<10 km) magma chamber,
causing convection and mixing between the incoming and resident magmas. These processes may trigger dyke propagation and further
magma rise, inducing long-term (days to months) volcano deformation, seismic swarms, gravity anomalies, and changes in the
composition of volcanic plumes and fumaroles, eventually culminating in an eruption. Although new magma injection into shallow
magma chambers can lead to hazardous event, such injection is still not systematically detected and recognized. Here, we present
the results of numerical simulations of magma convection and mixing in geometrically complex magmatic systems, and describe
the multiparametric dynamics associated with buoyant magma injection. Our results reveal unexpected pressure trends and pressure
oscillations in the Ultra-Long-Period (ULP) range of minutes, related to the generation of discrete plumes of rising magma.
Very long pressure oscillation wavelengths translate into comparably ULP ground displacements with amplitudes of order 10−4–10−2 m. Thus, new magma injection into magma chambers beneath volcanoes can be revealed by ULP ground displacement measured at
the surface. 相似文献
59.
Karla Donato Fook Antônio Miguel Vieira Monteiro Gilberto Câmara Marco Antônio Casanova Silvana Amaral 《Transactions in GIS》2009,13(4):379-399
Biodiversity researchers in different institutions deal with predictive models for species distribution. These models are useful for biodiversity conservation policies. Species distribution modelling tools need large datasets from different sources and use many algorithms. To improve biodiversity science, scientists need to share models, data and results, and should be able to reproduce experiments from others. This article presents a geoweb service architecture that supports sharing of modelling results and enables researchers to perform new modelling experiments. We show the feasibility of the proposed architecture by developing a set of prototype services, called Web Biodiversity Collaborative Modelling Services – WBCMS. They provide a set of geospatial web services that support the sharing of species distribution models. The article includes an example of a model instance that explains the WBCMS prototype. We believe that WBCMS shows how to set up a cooperative research network on biodiversity research. 相似文献
60.
Barros J Igrejas G Andrade M Radhouani H López M Torres C Poeta P 《Marine pollution bulletin》2011,62(6):1245-1248
Antibiotic resistance in bacteria is a growing problem that is not only restricted to the clinical setting but also to other environments such as marine species that harbor antibiotic resistant bacteria and therefore may serve as reservoirs for antibiotic-resistance genetic determinants. The aim of this study was to evaluate antibiotic resistance phenotypes in enterococci isolated from fecal samples of gilthead seabream and the associated mechanisms of resistance. A collection of 118 samples were analyzed and 73 enterococci were recovered. The strains showed high percentages of resistance to erythromycin and tetracycline (58.9% and 17.8%, respectively). Lower level of resistance (<13%) was detected for quinupristin-dalfopristin, ampicillin, high-level-gentamicin, high-level-streptomycin, high-level-kanamycin, ciprofloxacin and chloramphenicol. The erm(B), tet(L) or tet(M), aac(6′)-aph(2″) and aph(3′)-IIIa genes were shown in isolates resistant to erythromycin, tetracycline, high-level gentamicin and high-level kanamycin, respectively. Antibiotic resistance in natural microbiota is becoming a concern of human and environmental health. 相似文献