Topological redundancy and ‘small‐world’ patterns in a food web in a subtropical ecosystem of Brazil          下载免费PDF全文

Hugo Bornatowski  Rodrigo Barreto  Andrés F. Navia  Alberto Ferreira de Amorim 《Marine Ecology》2017,38(2)

According to graph theory, the frequency distribution of trophic interactions within a food web has deep structural implications, as it can highlight the presence of patterns associated with the web and indicate whether the properties of the web are independent of its size. A hypothesis is that ‘small‐world’ food webs are sensitive to the loss of species with the highest values. Therefore, the present work aimed to evaluate the degree to which a subtropical food web in Southern Brazil displays small‐world patterns and their resistance. As part of the assessment, we evaluated the topological redundancy values of species in the food web and then we simulated the exclusion of these species (such as sharks and sea birds), and also the exclusion of high centrality species (such as squids Loligo sp., portunid swimming crabs and the cutlassfish Trichiurus lepturus). The food web showed a ‘broad‐scale’ distribution of connections by node, and a small‐world pattern. As expected, a simplification of the network was observed after elimination of some species with high centrality. However, the food web was resistant to the loss of species with low topological redundancy, probably because these species occupy a high trophic level and do not participate in lots of routes within the food web. We highlight however, the importance of the application of multiple analyses to evaluate the importance of components in food webs, and fisheries management plans should consider both species of high centrality values and species with low topological redundancy.  相似文献   

Towards a spatial data infrastructure for technological disasters: an approach for the road transportation of hazardous materials     

Janaina Bezzerra Silva  Mariana A. Giannotti  Ana Paula C. Larocca  José Alberto Quintanilha 《GeoJournal》2017,82(2):293-310

Spatial data have been used for the environmental monitoring of the consequences of accidents that involve the transportation of hazardous chemical products. This spatial data infrastructure (SDI), which was created for the sharing and use of spatial data, is limited by the absence of policies to support its establishment. The main objective of this study was to explore the use of social network analysis (SNA) as a tool to identify spatial data sharing between organizations involved in the management of accidents related to road transport of hazardous materials (RTHM). In addition, to discuss the existing policies and institutional agreements, and to initiate a conceptual SDI framework for RTHM sector. In this context, the institutions that are involved with RTHM were identified and information concerning their interest in the use and sharing of spatial data via a SDI was collected through interviews and consolidated. The interviews were at 39 institutions with representative employees. The interview data were tabulated and entered into the UCINET software (2000 version) to calculate metrics of centrality. From the SNA, the flow of data among the participating institutions was identified through the visual representation of the spatial data sharing and use networks. Subsequently, the existing institutional agreements for spatial data sharing were analyzed and discussed. The compiled results enabled the proposal of a conceptual SDI framework to support the management of disasters involving RTHM, based on the application of SNA theory, and the development of a methodology that supports the analysis of interactions among the various actors of an SDI. The purpose is to facilitate the formulation of policies for the sharing of spatial data for decision-making and preventive disaster management. The results indicate that the 39 institutions share spatial data, but this sharing is not always predetermined by formal agreements. Furthermore, there is a strong demand, by the institutions involved in the management of RTHM accidents, regarding legal mechanisms governing the sharing of data for the purpose of producing maps that help to describe actions of preparedness, prevention, management and immediate relief involving RTHM incidents. Finally, it was possible to propose a conceptual framework with data that is considered essential for creating an SDI for RTHM.  相似文献   

GIS technology and models for assessing landslide hazard and risk   总被引：8，自引：1，他引：7  

Alberto Carrara  Richard J. Pike   《Geomorphology》2008,94(3-4):257

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PGA and structural dynamics input motion at a given site   总被引：1，自引：1，他引：0  

Fabio?CasciatiEmail author  Sara?Casciati  Alberto?Marcellini 《地震工程与工程振动(英文版)》2003,2(1):25-33

The computation of the representative ground motions, to be used as input for the dynamic analyses of a structure at a particular site, can be approached by several methods. The choice of the approach depends on two factors : the data available and the type of problem to be solved. This paper reports the experience of the authors in approaching a specific case study: the Southern Memnon Colossus, located in Luxor, Egypt. The results are of interest when the hazard analysis estimation in developing countries and the safeguard of cultural heritage are concerned. Monuments have to be treated as important structures, due to their historical and economical value. Hence, standard procedures of probabilistic seismic hazard analysis for the seismic classification of common buildings have to be disregarded. On the other hand, the consequences of the collapse of a monument are not comparable to those related to structures such as nuclear power plants and large dams, for which the deterministic seismic hazard analysis provides a straightforward framework for evaluation of the worst case ground motions. An “intermediate” approach, which requires a lower amount of input data with respect to the deterministic one, is adopted. Its stochastic component can capture significant characteristics of earthquakes, primarily the frequency contents which depend on the magnitude (often referred to as the earthquake scaling law). Supported by: European Union-ICA3-1999-00006  相似文献   

Scale radii and aggregation histories of dark haloes     

Eduard Salvador-Solé  Alberto Manrique  José María Solanes 《Monthly notices of the Royal Astronomical Society》2005,358(3):901-912

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Imaging polarimetry of comet Hale-Bopp (C/1995 O1) around perihelion     

Paolo Tanga  Alberto Cellino  Mario Di Martino 《Earth, Moon, and Planets》1997,78(1-3):359-364

The polarization distribution of the inner coma of comet Hale-Bopp was measured by CCD imaging around perihelion. The dust shell positions correlate well with relative maxima of polarization. The images taken in the I-band identify different shell systems, each showing individual polarization properties. This could be related to differences in the dust properties of the associated jets. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Experimental and Numerical Studies on the Seismic Response of R.C. Hollow Bridge Piers   总被引：3，自引：2，他引：1  

Gian?Michele?CalviEmail author  Alberto?Pavese  Alessandro?Rasulo  Davide?Bolognini 《Bulletin of Earthquake Engineering》2005,3(3):267-297

Appropriate seismic assessment of reinforced concrete bridges is an important challenge in structural engineering in consideration of the number and relevance of bridges built without applying advanced codes of practice and of the strategic role of transportation networks in modern economy. This paper focuses on some relevant aspects of the damage development and collapse modes of hollow piers, as commonly designed in the past. The following aspects have been considered: absence of confinement, inadequate shear strength, shifting of the critical section, insufficient length of lap splices. A series of experimental tests has been designed and performed; the capacity of predicting appropriate results of formulations recommended in codes of practice or proposed in recent research documents has been checked comparing experimental and analytical results.  相似文献   

Extraterrestrial hydrogeology     

Victor?R.?BakerEmail author  James?M.?Dohm  Alberto?G.?Fairén  Ty?P.?A.?Ferré  Justin?C.?Ferris  Hideaki?Miyamoto  Dirk?Schulze-Makuch 《Hydrogeology Journal》2005,13(1):51-68

Subsurface water processes are common for planetary bodies in the solar system and are highly probable for exoplanets (planets outside the solar system). For many solar system objects, the subsurface water exists as ice. For Earth and Mars, subsurface saturated zones have occurred throughout their planetary histories. Earth is mostly clement with the recharge of most groundwater reservoirs from ample precipitation during transient ice- and hot-house conditions, as recorded through the geologic and fossilized records. On the other hand, Mars is mostly in an ice-house stage, which is interrupted by endogenic-driven activity. This activity catastrophically drives short-lived hydrological cycling and associated climatic perturbations. Regional aquifers in the Martian highlands that developed during past, more Earth-like conditions delivered water to the northern plains. Water was also cycled to the South Polar Region during changes in climate induced by endogenic activity and/or by changes in Mars orbital parameters. Venus very likely had a warm hydrosphere for hundreds of millions of years, before the development of its current extremely hot atmosphere and surface. Subsequently, Venus lost its hydrosphere as solar luminosity increased and a run-away moist greenhouse took effect. Subsurface oceans of water or ammonia-water composition, induced by tidal forces and radiogenic heating, probably occur on the larger satellites Europa, Ganymede, Callisto, Titan, and Triton. Tidal forces operating between some of the small bodies of the outer solar system could also promote the fusion of ice and the stability of inner liquid-water oceans.

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Resumen Los procesos hídricos subsuperficiales son comunes en cuerpos planetarios del sistema solar y son altamente probables para exoplanetas (planetas fuera del sistema solar). Para muchos cuerpos del sistema solar, el agua subsuperficial existe como hielo. Para la Tierra y Marte han ocurrido zonas saturadas subsuperficiales a través de sus historias planetarias. La Tierra es principalmente generosa con la recarga de la mayoría de reservorios de aguas subterráneas a partir de amplia precipitación reconocida en condiciones transitorias calientes y heladas, tal y como aparece en los registros fósiles y geológicos. Por otro lado, Marte se encuentra principalmente en una etapa de cámara de hielo la cual es interrumpida por actividad de tipo endogénico. Esta actividad pone en funcionamiento catastróficamente ciclos hidrológicos de vida corta y perturbaciones climáticas asociadas. Acuíferos regionales en las montañas de Marte que se desarrollaron en el pasado en condiciones similares a la Tierra distribuyen agua a las planicies del norte. El agua ha sido transportada hacia el sur de la región polar durante cambios en el clima inducidos por actividad endogénica y/o cambios en los parámetros orbitales de Marte. Venus muy probablemente tuvo una hidrósfera caliente durante cientos de millones de años, antes de que se desarrollara su atmósfera y superficie actual extremadamente caliente. Subsecuentemente, Venus perdió su hidrósfera a medida que la luminosidad solar aumentó y un efecto de invernadero húmedo escapatorio se llevó a cabo. Océanos subsuperficiales de composición agua o amoniaco-agua, inducidos por fuerzas de marea y calentamiento radiogénico, probablemente ocurren en los satélites más grandes como Europa, Ganimeda, Callisto, Titan y Triton. Las fuerzas de marea que operan entre los cuerpos pequeños del sistema solar externo podrían también promover la fusión de hielo y la estabilidad de líquido interno-aguas de los océanos.

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Résumé Les processus de subsurface impliquant leau sont communs pour les corps planétaires du système solaire et sont très probables sur les exoplanètes (planètes en dehors du système solaire). Pour plusieurs objets du systèmes solaire, leau de subsurface est présente sous forme de glace. Pour la Terre et Mars, les zones saturées de subsurface apparaissent à travers toute leur histoire planétaire. La Terre est particulièrement clémente avec la recharge des réservoirs, avec de amples précipitations, des conditions glaciaires et de fortes chaleurs, comme latteste les enregistrements géologiques et paléontologiques. Dun autre côté, Mars se trouve dans une phase essentiellement glaciaire, qui est interrompue par des activités contraintes par les phénomènes endogéniques. Cette activité conduit de manière catastrophique à des cycles hydrologiques et à des perturbations climatiques brutaux. Les aquifères régionaux dans les haute terres martiennes qui se sont formés dans des conditions similaires aux conditions terrestres, alimentent les plaines du Nord. Leau a également été déplacée vers le Pôle Sud martien durant des changements marqués par une forte activité endogénique et une modification des paramètres de lorbite de Mars. Venus possèdait vraisemblablement une hydrosphère chaude durant des millions dannée, avant le développement de son atmosphère et sa surface particulièrement chaude. Par après Venus a perdit son hydrosphère alors que la luminosité solaire augmentait et quune humidité liée à un effet de serre sinstallait. Les océans de subsurface deau ou deau ammoniacale, induits par les forces de marée et le chauffage radiogénique, apparaissent probablement sur les satellites les plus importants (Europa, Ganymede, Callisto, Titan, Triton). Les forces de marée entre les petits corps externes du système solaire peuvent également occasionner la fusion de glace et la stabilité des océans internes deau liquide.

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Do we have enough pieces of the jigsaw to integrate CO2 fluxes in the coastal ocean?   总被引：1，自引：0，他引：1  

Alberto V. Borges 《Estuaries and Coasts》2005,28(1):3-27

Annually integrated air-water CO₂ flux data in 44 coastal environments were compiled from literature. Data were gathered in 8 major ecosystems (inner estuaries, outer estuaries, whole estuarine systems, mangroves, salt marshes, coral reefs, upwelling systems, and open continental shelves), and up-scaled in the first attempt to integrate air-water CO₂ fluxes over the coastal ocean (26×10⁶ km²), taking into account its geographical and ecological diversity. Air-water CO₂ fluxes were then up-scaled in global ocean (362×10⁶ km²) using the present estimates for the coastal ocean and those from Takahashi et al. (2002) for the open ocean (336×10⁶ km²). If estuaries and salt marshes are not taken into consideration in the up-scaling, the coastal ocean behaves as a sink for atmospheric CO₂(−1.17 mol C m⁻² yr⁻¹) and the uptake of atmospheric CO₂ by the global ocean increases by 24% (−1.93 versus −1.56 Pg C yr⁻¹). The inclusion of the coastal ocean increases the estimates of CO₂ uptake by the global ocean by 57% for high latitude areas (−0.44 versus −0.28 Pg C yr⁻¹) and by 15% for temperate latitude areas (−2.36 versus −2.06 Pg C yr⁻¹) At subtropical and tropical latitudes, the contribution from the coastal ocean increases the CO₂ emission to the atmosphere from the global oceam by 13% (0.87 versus 0.77 Pg C yr⁻¹). If estuaries and salt marshes are taken into consideration in the upscaling, the coastal ocean behaves as a source for atmospheric CO₂ (0.38 mol C m⁻² yr⁻¹) and the uptake of atmospheric CO₂ from the global ocean decreases by 12% (−1.44 versus −1.56 Pg C yr⁻¹) At high and subtropical and tropical latitudes, the coastal ocean behaves as a source for atmospheric CO₂ but at temperate latitudes, it still behaves as a moderate CO₂ sink. A rigorous up-scaling of air-water CO₂ fluxes in the coastal ocean is hampered by the poorly constrained estimate of the surface area of inner estuaries. The present estimates clearly indicate the significance of this biogeochemically, highly active region of the biosphere in the global CO₂ cycle.  相似文献   

Cultural heritage and geological hazards: the case of the Calomini hermitage in Tuscany (Italy)   总被引：1，自引：0，他引：1  

Giacomo D’Amato Avanzi  Daria Marchetti  Alberto Puccinelli 《Landslides》2006,3(4):331-340

The Calomini hermitage is located on a steep slope, below an 80- to 130-m-high hanging rock wall. The hermitage, a significant example of religious architecture, has been a pilgrimage place since the Middle Ages. The monastery, completed by the tenth century, is built into the rock mass for more than half of its length. The stability and safety of the complex are threatened by stability problems in the rock slope. Structural and geotechnical investigations were carried out, showing the potential for rock blocks slides, particularly under dynamic conditions, with the fall of middle size blocks. Recently, some remedial works have been carried out, and wire meshes have been hung on the rock wall. Nevertheless, a significant portion of the Calomini hermitage area may be still dangerous and exposed to severe landslide hazard. Therefore, further research and countermeasures are necessary to protect a very important item of Italian cultural and architectural heritage.  相似文献