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1.
This paper establishes an anisotropic nonlinear damage model in strain space to describe the behavior of jointed rock and applies it to mechanical analysis of tunnelling. This work focuses on rate-independent and small-deformation behavior during static isothermal processes. The prime results include: (1) the properties of damage-dependent elasticity tensors based on geological information of the jointed rock mass; (2) the damage evolution law presented on the basis of thermodynamics and combined with endochronic theory; and (3) the global damage tensor based on the work-equivalence principle and the local geological data of multi-joint sets. Finally the numerical results of a tunnel intersection in jointed rock is presented to illustrate the mechanical behavior of this model. 相似文献
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Marc Pons Peter A Johnson Martí Rosas Eric Jover 《International journal of geographical information science》2014,28(12):2474-2494
One main argument for modeling socio-ecological systems is to advance the understanding of dynamic correlations between various human and environmental factors, including impacts and responses to environmental change. We explore the shift in skier distribution among ski resorts taking into account the behavioral adaptation of individuals due to the impact of climate change on snow conditions. This analysis is performed at a regional scale by means of a coupled gravity and georeferenced agent-based model. Four different scenarios are considered. Two scenarios assume an increase of winter mean temperature of +2°C and +4°C, respectively, taking into account only natural snow conditions. Two additional scenarios add the effect of snowmaking to enhance the natural snow depth and extend the skiing season in the +2°C and +4°C base scenarios. Results show differing vulnerability levels, allowing the classification of ski resorts into three distinct groups: (1) highly vulnerable ski resorts with a strong reduction in visitors attendance for all climate change scenarios, characterized by unfavorable geographical and attractiveness conditions, making it difficult to ensure snow availability in the future; (2) low vulnerability ski resorts, with moderate reduction in season length during a high climate change scenario but no reduction (or even an increase) in a low one, characterized by ski resorts with a medium capacity and attractiveness to ensure enough snow conditions and capture skiers from other ski resorts; and (3) resilient ski resorts, with good conditions to ensure future snow-reliable seasons and outstanding attractiveness, allowing them to offer longer ski seasons than their competitors and potentially attracting skiers from other closed or marginal resorts. Ski resorts included in this last group increase their skier attendance in all climate change scenarios. Although similar studies in the literature foretell a significant reduction of the ski market in the near future, another probable effect outlined in this study is a redefinition of this market due to a redistribution of skiers, from vulnerable ski resorts to more resilient ones. 相似文献
3.
Kunito T Nakamura S Ikemoto T Anan Y Kubota R Tanabe S Rosas FC Fillmann G Readman JW 《Marine pollution bulletin》2004,49(7-8):574-587
Concentrations of trace elements (V, Cr, Mn, Fe, Co, Cu, Zn, Ga, As, Se, Rb, Sr, Mo, Ag, Cd, Sb, Cs, Ba, T-Hg, Org-Hg, Tl and Pb) were determined in liver samples of estuarine dolphin (Sotalia guianensis; n = 20), Franciscana dolphin (Pontoporia blainvillei; n = 23), Atlantic spotted dolphin (Stenella frontalis; n = 2), common dolphin (Delphinus capensis; n = 1) and striped dolphin (Stenella coeruleoalba; n = 1) incidentally caught along the coast of Sao Paulo State and Parana State, Brazil, from 1997 to 1999. The hepatic concentrations of trace elements in the Brazilian cetaceans were comparable to the data available in literature on marine mammals from Northern Hemisphere. Concentrations of V, Se, Mo, Cd, T-Hg and Org-Hg increased with increasing age in liver of both estuarine and Franciscana dolphins. Very high concentrations of Cu (range, 262-1970 microg/g dry wt.) and Zn (range, 242-369 microg/g dry wt.) were observed in liver of sucklings of estuarine dolphin. Hepatic concentrations of V, Se, T-Hg, Org-Hg and Pb were significantly higher in estuarine dolphin, whereas Franciscana dolphin showed higher concentrations of Mn, Co, As and Rb. Ratio of Org-Hg to T-Hg in liver was significantly higher in Franciscana dolphin than estuarine dolphin, suggesting that demethylation ability of methyl Hg might be lower in liver of Franciscana than estuarine dolphins. High hepatic concentrations of Ag were found in some specimens of Franciscana dolphin (maximum, 20 microg/g dry wt.), and 17% of Franciscana showed higher concentrations of Ag than Hg. These samples with high Ag concentration also exhibited elevated hepatic Se concentration, implying that Ag might be detoxified by Se in the liver. Higher correlation coefficient between (Hg+0.5 Ag) and Se than between Hg and Se and the large distribution of Ag in non-soluble fraction in nuclear and mitochondrial fraction of the liver also suggests that Ag might be detoxified by Se via formation of Ag2Se in the liver of Franciscana dolphin. 相似文献
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Ramón A. López‐Pérez Luis E. Calderón‐Aguilera Héctor Reyes‐Bonilla José D. Carriquiry Pedro Medina‐Rosas Amilcar L. Cupul‐Magaña María D. Herrero‐Pérezrul Héctor A. Hernández‐Ramírez Miguel Á. Ahumada‐Sempoal Betsabe M. Luna‐Salguero 《Marine Ecology》2012,33(4):407-416
Corals in the Eastern Pacific extend south from the Gulf of California to Ecuador and oceanic Chile, and west from Colombia to Clipperton Atoll. Nevertheless, large stretches of the Mexican Pacific remain fundamentally unstudied. Therefore, to assess the current conditions of coral communities, a coastal fringe ～300 km long (17°40′ N, 101°39′ W to 16°46′ N, 99°49′ W) was surveyed within the Southern Mexican Pacific, between 2005 and 2009. Fifteen stony coral species were identified at 13 coral communities and six Pocillopora‐dominated fringing reefs, with Pocillopora verrucosa and Pocillopora damicornis the primary contributing taxa. Reef development was identified in embayments or behind rocks or islands that offered shelter from northern and northwestern winds. Observations of Pocillopora effusus, Pocillopora inflata, Porites lobata, Pavona clavus, and Pavona varians expanded the species known geographic ranges by several degrees of latitude, suggesting reef building fauna comprised a mixture of widespread and relatively rare Eastern Pacific corals. Results indicated greater live coral cover in the Ixtapa‐Zihuatanejo area (15–73%) than in the Acapulco localities, which had high algal dominance; the reefs in the latter region exhibited high erosion. Regional differences are likely the result of long‐standing anthropogenic pressures around Acapulco since 1950, when it became an important tourist destination. This paper is the first detailed report of ecologically stressed corals and coral reefs from the state of Guerrero on the Mexican Southern Pacific coast. 相似文献
6.
R. Moritz L. Fontboté J. Spangenberg S. Rosas Z. Sharp D. Fontignie 《Mineralium Deposita》1996,31(3):147-162
A combined Sr, O and C isotope study has been carried out in the Pucará basin, central Peru, to compare local isotopic trends of the San Vicente and Shalipayco Zn-Pb Mississippi Valley-type (MVT) deposits with regional geochemical patterns of the sedimentary host basin. Gypsum, limestone and regional replacement dolomite yield 87Sr/86Sr ratios that fall within or slightly below the published range of seawater 87Sr/86Sr values for the Lower Jurassic and the Upper Triassic. Our data indicate that the Sr isotopic composition of seawater between the Hettangian and the Toarcian may extend to lower 87Sr/86Sr ratios than previously published values. An 87Sr-enrichment is noted in (1) carbonate rocks from the lowermost part of the Pucará basin, and (2) different carbonate generations at the MVT deposits. This indicates that host rocks at MVT deposits and in the lower-most part of the carbonate sequence interacted with 87Srenriched fluids. The fluids acquired their radiogenic nature by interaction with lithologies underlying the carbonate rocks of the Pucará basin. The San Ramón granite, similar Permo-Triassic intrusions and their clastic derivatives in the Mitu Group are likely sources of radiogenic 87Sr. The Brazilian shield and its erosion products are an additional potential source of radiogenic 87Sr. Volcanic rocks of the Mitu Group are not a significant source for radiogenic 87Sr; however, molasse-type sedimentary rocks and volcaniclastic rocks cannot be ruled out as a possible source of radiogenic 87Sr. The marked enrichment in 87Sr of carbonates toward the lower part of the Pucará Group is accompanied by only a slight decrease in
18O values and essentially no change in
13C values, whereas replacement dolomite and sparry carbonates at the MVT deposits display a coherent trend of progressive 87Sr-enrichment, and 18O- and 13C-depletion. The depletion in 18O in carbonates from the MVT deposits are likely related to a temperature increase, possibly coupled with a 18O-enrichment of the ore-forming fluids. Progressively lower
13C values throughout the paragenetic sequence at the MVT deposits are interpreted as a gradually more important contribution from organically derived carbon. Quantitative calculations show that a single fluid-rock interaction model satisfactorily reproduces the marked 87Sr-enrichment and the slight decrease in
18O values in carbonate rocks from the lower part of the Pucará Group. By contrast, the isotopic covariation trends of the MVT deposits are better reproduced by a model combining fluid mixing and fluid-rock interaction. The modelled ore-bearing fluids have a range of compositions between a hot, saline, radiogenic brine that had interacted with lithologies underlying the Pucará sequence and cooler, dilute brines possibly representing local fluids within the Pucará sequence. The composition of the local fluids varies according to the nature of the lithologies present in the neighborhood of the different MVT deposits. The proportion of the radiogenic fluid in the modelled fluid mixtures interacting with the carbonate host rocks at the MVT deposits decreases as one moves up in the stratigraphic sequence of the Pucará Group. 相似文献
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The coral communities of the Islas Marias archipelago,Mexico: structure and biogeographic relevance to the Eastern Pacific 
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下载免费PDF全文 Andrés López‐Pérez Amilcar Cupul‐Magaña Miguel Angel Ahumada‐Sempoal Pedro Medina‐Rosas Héctor Reyes‐Bonilla María Dinorah Herrero‐Pérezrul Cristóbal Reyes‐Hernández Julio Lara‐Hernández 《Marine Ecology》2016,37(3):679-690
Various authors have suggested that the Islas Marias archipelago, Mexico, may play a significant biogeographic role in the dispersal of Indo Pacific coral species into the Eastern Pacific; however, the coral communities of this archipelago have received scarce attention to date. Here, we first addressed coral community structure across the islands and, by employing ordination analysis, minimum spanning tree and particle‐tracking experiments, used this information to evaluate the relevance of the archipelago for coral dispersal. Twenty‐four coral communities were recorded in the archipelago. Coral cover varied significantly among islands: Maria Cleofas had large values (38.5%), intermediate values were observed for Maria Madre (26.5%) and Maria Magdalena (22.84%), and relatively low values were recorded for San Juanito (18.5%). Coral communities mainly consisted of Pocillopora (57.3%) and Porites (25.5%) species, while species of Pavona (16%) and Psammocora (0.6%) made relatively minor contributions. Thirteen stony coral species were identified in the archipelago; of these Psammocora profundacella and Pavona duerdeni represent new records. Ordination analysis, minimum spanning tree and particle‐tracking experiments suggested similar connecting paths in the studied area; in general, the Islas Marias stands as a route for coral dispersal of Indo Pacific species into the Northeastern Pacific. In a regional context, the Islas Marias has three major biogeographic implications to coral dispersal: (i) the archipelago stands as a major stepping stone for the transport of species and individuals among the Revillagigedo archipelago, the Gulf of California and the tropical Mexican Pacific; (ii) the Islas Marias may play a seminal role in maintaining the genetic connectivity between southern and northern coral populations along the Mexican Pacific and (iii) because of its relatively pristine status and low levels of human impact, the archipelago may potentially serve as a source of coral propagules for ecosystem recovery in the Gulf of California and along the Pacific coast of the Mexican mainland following natural and/or human induced perturbations. 相似文献
8.
Rigoberto Rosas‐Luis María de Lourdes Jimnez Badillo Lucia Montoliu‐Elena Piedad S. Morillo‐Velarde 《Marine Ecology》2019,40(1)
Octopuses are active predators that feed on a wide range of prey including crustaceans, fishes, and mollusks. They are important components of coral reef systems and support local and artisanal fisheries in the Gulf of México. Octopus insularis has been found to be one of the most relevant components in catches from the coral reef system of Veracruz in the southwestern Gulf of Mexico, and its role in the ecosystem requires assessment. To corroborate the morphological identification of O. insularis, six octopuses were identified by genetic methods. And to understand the trophic relationships between this octopus species and its prey, 394 octopuses caught during 2016 and 2017 by an artisanal fleet were sampled and their stomach contents analyzed. Results showed that crustaceans are the most frequently consumed group, with the genera Mithraculus and Etisus being the most important in the diet. Fishes, bivalves, and gastropods were identified as uncommon prey items in the diet. Their presence in the stomachs could be related to the movement of this octopus outside of the coral reef. Considering that our samples were of medium‐ and large‐sized individuals, cannibalism could be discarded for O. insularis in this size range in the Veracruz reef system. These findings suggest a generalist and opportunistic predation of O. insularis on the most abundant and available prey in the study area, namely the crustaceans. These represents an effective transfer of biomass from the low trophic levels to top predators in the coral reef system. 相似文献
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Thierry Sempere Gabriel Carlier Pierre Soler Michel Fornari Víctor Carlotto Javier Jacay Oscar Arispe Didier Nraudeau Jos Crdenas Silvia Rosas Nstor Jimnez 《Tectonophysics》2002,345(1-4)
Integrated studies and revisions of sedimentary basins and associated magmatism in Peru and Bolivia (8–22°S) show that this part of western Gondwana underwent rifting during the Late Permian–Middle Jurassic interval. Rifting started in central Peru in the Late Permian and propagated southwards into Bolivia until the Liassic/Dogger, along an axis that coincides with the present Eastern Cordillera. Southwest of this region, lithospheric thinning developed in the Early Jurassic and culminated in the Middle Jurassic, producing considerable subsidence in the Arequipa basin of southern Peru. This 110-Ma-long interval of lithospheric thinning ended 160 Ma with the onset of Malm–earliest Cretaceous partial rift inversion in the Eastern Cordillera area.The lithospheric heterogeneities inherited from these processes are likely to have largely influenced the distribution and features of younger compressional and/or transpressional deformations. In particular, the Altiplano plateau corresponds to a paleotectonic domain of “normal” lithospheric thickness that was bounded by two elongated areas underlain by thinned lithosphere. The high Eastern Cordillera of Peru and Bolivia results from Late Oligocene–Neogene intense inversion of the easternmost thinned area. 相似文献
10.
Marc-André Gutscher Stephane Dominguez Graham K. Westbrook Pascal Gente Nathalie Babonneau Thierry Mulder Eliane Gonthier Rafael Bartolome Joaquim Luis Filipe Rosas Pedro Terrinha 《Marine and Petroleum Geology》2009,26(5):647-659
The Gulf of Cadiz lies astride the complex plate boundary between Africa and Eurasia west of the Betic-Rif mountain belt. We report on the results of recent bathymetric swathmapping and multi-channel seismic surveys carried out here. The seafloor is marked by contrasting morphological provinces, spanning the SW Iberian and NW Moroccan continental margins, abyssal plains and an elongate, arcuate, accretionary wedge. A wide variety of tectonic and gravitational processes appear to have shaped these structures. Active compressional deformation of the wedge is suggested by folding and thrusting of the frontal sedimentary layers as well as basal duplexing in deeper internal units. There is evidence for simultaneous gravitational spreading occurring upslope. The very shallow mean surface and basal slopes of the accretionary wedge (1° each) indicate a very weak decollement layer, geometrically similar to the Mediterranean Ridge accretionary complex. Locally steep slopes (up to 10°) indicate strongly focused, active deformation and potential gravitational instabilities. The unusual surface morphology of the upper accretionary wedge includes “raft-tectonics” type fissures and abundant sub-circular depressions. Dissolution and/or diapiric processes are proposed to be involved in the formation of these depressions. 相似文献