Construction and analysis of higher order finite difference schemes for the 1D wave equation     

Laurent Anné  Patrick Joly  Quang Huy Tran 《Computational Geosciences》2000,4(3):207-249

In this article, we propose to: 1. Establish most of the properties conjectured in [2] about the higher order finite difference approximation of the 1D Laplace operator. 2. Generalize to any order the fourth-order accurate scheme in space and time of Shubin and Bell [20] and Cohen [6]. For this new family of 2m–2m schemes, we establish, via elementary mathematics, various stability and dispersion results that are helpful to compare these schemes to the 2–2m schemes of Anné et al. [2]. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Design of an MTBE Remediation Technology Evaluation   总被引：1，自引：0，他引：1  

Ann Azadpour-Keeley  Michael J. Barcelona 《Ground Water Monitoring & Remediation》2006,26(2):103-113

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The use of infauna by juvenile Penaeus aztecus Ives and Penaeus setiferus (Linnaeus)     

Teresa Ann McTigue  Roger J. Zimmerman 《Estuaries and Coasts》1998,21(1):160-175

Penaeus aztecus Ives, the brown shrimp, and Penaeus setiferus (Linnaeus), the white shrimp, co-occur in Texas salt marshes as juveniles. Although their life cycles are similar, evidence indicates that the species utilize different resources for the primary faunal element of their diets. Prey selection and growth studies have shown that brown shrimp successfully remove infauna from natural sediment. Further, a diet of polychaetes, whether alone or in combination with algae, produced growth in the species. Brown shrimp appear to be trophically linked to infaunal populations, thus the structure and dynamics of the benthic community may directly affect local brown shrimp productivity. Areas dominated by surface-dwelling polychaetes as opposed to deep burrowers may provide more accessible foraging opportunities for juvenile brown shrimp. By contrast, white shrimp neither removed infauna nor grew to a significant degree when provided polychaetes or amphipods as food. White shrimp are omnivorous but do not rely on infaunal material to the same extent as brown shrimp. The primary faunal element in the diet of white shrimp has not yet been identified. The dietary differences between the two species may play a role in determining which species dominates in regions with varying marsh accessibility. Although not the only factors influencing penaeid survival and growth, prey choice and availability may greatly affect production and local success of penaeid populations. *** DIRECT SUPPORT *** A01BY081 00013  相似文献   

Effects of menhaden predation of plankton populations in Narragansett Bay, Rhode Island     

Ann G. Durbin  Edward G. Durbin 《Estuaries and Coasts》1998,21(3):449-465

The Atlantic menhaden,Brevoortia tyrannus, is an abundant plankton-feeding fish that undertakes extensive seasonal migrations, moving from overwintering locations offshore south of Cape Hatteras to the mid-Atlantic Bight and New England inshore waters during spring and summer. A bioenergetic model, based on field and laboratory studies, shows that when large numbers of menhaden enter Narragansett Bay, Rhode Island, during spring and early summer, they significantly influence plankton populations through size-selective grazing and nutrient regeneration. A population biomass of 9.1×10⁶ kg of menhaden feeding for 12 h each day in the upper bay would result, in a substantial reduction of the instantaneous growth rate of the >20-μm phytoplankton. Instantaneous growth rates of zooplankton would be negative if the same population of menhaden was present, resulting in a reduction in the biomass of zooplankton. Given the ambient phytoplankton and zooplankton populations, menhaden could achieve the seasonal growth measured in Narragansett Bay during 1976 by feeding on average about 5 h d^?1. Daily nitrogen excretion rates of the 9.1×10⁶ kg menhaden population were 56.4% of the mean standing stock of ammonia-N in the upper bay. Because menhaden travel in schools their effects are likely to be intense but strongly localized, increasing spatial heterogeneity in the ecosystem. When the fish migrate southward in the fall they transfer between 3.3% and 6.2% of the nitrogen exported annually from the bay.  相似文献   

The barometric tides at Zürich and on the summit of Säntis     

Bernhard Haurwitz  Ann D. Cowley 《Pure and Applied Geophysics》1975,113(1):355-364

Summary Lunar barometric tidal determinations (L ₂) have been made by the Chapman-Miller method for Zürich (493 m) and Säntis (2000 m) based on 49 years' data. The seasonal variations ofL ₂ are much larger at Zürich than on the Säntis summit. However, a comparison with the five other pairs of stations for which tidal determinations at different altitudes, but short horizontal distances, are available do not indicate that this result is as an altitude effect, nor do they show any other systematic differences betweenL ₂ at the lower and the higher station. The solar tidal determinations agree well with those made byEggenberger (1944) and fit in with those obtained for other stations. From the difference between the pressure oscillations at Zürich and on Säntis the corresponding meantemperature oscillations of the air column between the two stations has been computed.The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献   

Vital and mortal staining of algae in the presence of chlorine-produced oxidants     

Ann E. Reynolds  Gail B. Mackiernan  Shirley D. Van Valkenburg 《Estuaries and Coasts》1978,1(3):192-196

Evans blue and neutral red were tested as mortal and vital stains respectively for eight estuarine algal species which had been exposed to chlorine-produced oxidants in a continuous-flow system. The effect of CPO on staining with Evans blue was negligible. High concentrations of CPO affected staining with neutral red in several instances; this is probably due to CPO-induced mortality of test organisms during the exposure or staining period. Neutral red leached fromSkeletonema costatum andOlisthodiscus luteus before the end of the staining period. Staining ofDunaliella tertiolecta with neutral red proceeded more slowly. Evens blue, which was incorporated quickly and remained in the cells, is recommended for live-dead determinations for all species examined exceptNitzschia closterium, for which neutral red should be used. Neither stain was effective onMychonastes ruminatus (Simpson and Van Valkenburg 1978).  相似文献   

Macrofauna along the Sudanese Red Sea coast: potential effect of mangrove clearance on community and trophic structure          下载免费PDF全文

Rasha A. O. Sabeel  Jeroen Ingels  Ellen Pape  Ann Vanreusel 《Marine Ecology》2015,36(3):794-809

Mangroves along the Sudanese Red Sea coast are under constant anthropogenic pressure. To better understand the influence of mangrove clearance on the intertidal benthic community, we investigated the composition, biodiversity and standing stock of the macrofauna communities at high‐, mid‐ and low‐water levels in three contrasting habitats: a bare sand flat, a cleared mangrove and an intact mangrove. In addition, a community‐wide metric approach based on taxon‐specific carbon and nitrogen isotope values was used to compare the trophic structure between the three habitats. The habitats differed significantly in terms of macrofaunal standing stock, community composition and trophic structure. The high‐ and mid‐water levels of the intact mangroves showed a distinct macrofaunal community characterized by elevated densities and biomass, largely governed by higher decapod and gastropod abundances. Diversity was similar for cleared and intact mangroves, but much lower for the bare sand flat. Community‐wide metrics indicated highest trophic diversity and community niche breadth in the intact mangroves. Differences between the cleared and intact mangroves can be partly attributed to differences in sediment characteristics resulting from mangrove clearance. These results suggest a significant impact of mangrove clearance on the macrofaunal community and trophic structure. This study calls for further investigations and management actions to protect and restore these habitats, and ensure the survival of this ecologically valuable coastal ecosystem.  相似文献   

Erratum to: Interaction between groundwater, the hyporheic zone and a Chalk stream: a case study from the River Lambourn, UK     

David J. Allen  W. George Darling  Daren C. Gooddy  Daniel J. Lapworth  Andrew J. Newell  Ann T. Williams  Debbie Allen  Corinna Abesser 《Hydrogeology Journal》2010,18(5):1301-1301

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Scenarios on future land changes in the West African Sahel     

Eric F. Lambin  Sarah Ann Lise D’haen  Ole Mertz  Jonas Østergaard Nielsen  Kjeld Rasmussen 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2014,114(1):76-83

In an attempt to anticipate possible futures of drylands of West Africa in the face of rapid socio-economic and environmental changes, we developed four scenarios based on recent survey data, the literature and our knowledge of the region. The four scenarios are inspired by those developed by the Millennium Ecosystem Assessment: (1) ‘downward spiral’ characterized by rapid climate change, expansion of agriculture and chaotic urban growth; (2) ‘integrated economy’ with integrated land management, food production for local markets and rural–urban exchanges; (3) ‘open doors’ characterized by large-scale out-migrations, land grabbing by foreign companies and development aid and (4) ‘climate change mitigation’ with an increase in biofuel crops, land management for carbon capture and development of off-farm activities. We conclude that the Sahel region is most likely moving away from being a highly climate-dependent region based on agriculture towards a more open and diversified economy. West African countries have to find a balance between the new opportunities and risks created by economic globalization.  相似文献   

Trophic ecology of Pomatoschistus microps within an intertidal bay (Roscoff,France), investigated through gut content and stable isotope analyses     

Jean‐Charles Leclerc  Pascal Riera  Laure M.‐L. J. Noël  Cédric Leroux  Ann C. Andersen 《Marine Ecology》2014,35(2):261-270

The diet of Pomatoschistus microps has been studied using both gut content and stable isotope analyses. In the Roscoff Aber Bay (Brittany, France), this fish is commonly found on sandy muddy intertidal flats. Gut content analyses were also interpreted using trophic indices. Owing to the large diversity of prey consumed, these indices emphasised the opportunistic feeding behaviour of P. microps. Here, this species fed mainly on endofauna with meiofauna being of high relative importance. The main biotic components of its trophic habitat, characterized by δ¹³C and δ¹⁵N, provided evidence of a major trophic pathway based on drift Enteromorpha sp. Trophic positions estimated by both diet analyses and isotopic analyses led to similar results. In this bay, P. microps is a first‐order predator with a low degree of omnivory. Despite a preferential consumption of the amphipod Corophium arenarium, we assumed that this goby behaves as a generalist feeding on a uniform variety of endofauna taxa.  相似文献