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Mirghani B.Y.,6955 Union Park Center | Mirghani B.Y.,North Carolina State University | Tryby M.E.,North Carolina State University | Tryby M.E.,Ecosystems Research Division | And 4 more authors.
Journal of Computing in Civil Engineering | Year: 2010

Many engineering and environmental problems that involve the determination of unknown system characteristics from observation data can be categorized as inverse problems. A common approach undertaken to solve such problems is the simulation-optimization approach where simulation models are coupled with optimization or search methods. Simulation-optimization approaches, particularly in environmental characterization involving natural systems, are computationally expensive due to the complex three-dimensional simulation models required to represent these systems and the large number of such simulations involved. Emerging grid computing environments (e.g., TeraGrid) show promise for improving the computational tractability of these approaches. However, harnessing grid resources for most computational applications is a nontrivial problem due to the complex hierarchy of heterogeneous and geographically distributed resources involved in a grid. This paper reports and discusses the development and evaluation of a grid-enabled simulation-optimization framework for solving environmental characterization problems. The framework is designed in a modular fashion that simplifies coupling with simulation model executables, allowing application of simulation-optimization approaches across problem domains. The framework architecture utilizes standard communications protocols and the message passing interface with an application programming interface to establish a connection between a centralized search application and simulation models running on TeraGrid resources. Sets of performance and scalability results for solving a groundwater source history reconstruction (SHR) problem are presented. The results show that for a given set of resources, parameters controlling the granularity at various levels of parallelism play an important role in the overall parallel performance. A production run for solving the SHR problem using three geographically distributed grid resources indicates that even in a cross-site grid environment a factor of 90 speedup is possible using 140 computer processors. © 2010 ASCE. Source


Golden H.E.,Ecosystems Research Division | Boyer E.W.,Pennsylvania State University | Brown M.G.,Cornell University | Elliott E.M.,University of Pittsburgh | Lee D.K.,Seoul National University
Water Resources Research | Year: 2010

Assessing the effects of atmospheric nitrogen (N) deposition on surface water quality requires accurate accounts of total N deposition (wet, dry, and cloud vapor); however, dry deposition is difficult to measure and is often spatially variable. Affordable passive sampling methods are available for estimating "hot spots" and spatial variations of gaseous dry N deposition (i.e., nitrogen dioxide (NO2) and ammonia (NH 3)), though few viable methods for estimating the deposition from nitric acid (HNO3) gas using passive sampling techniques exist. We consider passive sampling approaches for assessing spatial patterns of dry atmospheric N deposition across watersheds. We describe a method for constructing an inexpensive passive sampler (for less than $12 per unit) for monitoring spatial variations in the magnitude of HNO3 in the atmosphere. We demonstrate the applicability of passive samplers for use in watershed biogeochemical research and water quality management through a review of previous applications and via our own case study of the South Korean peninsula. © Copyright 2008 by the American Geophysical Union. Source


de Graff J.V.,U.S. Department of Agriculture | Sidle R.C.,Ecosystems Research Division | Ahmad R.,University of the West Indies | Scatena F.N.,University of Pennsylvania
Environmental Earth Sciences | Year: 2012

Worldwide concern for continuing loss of montane forest cover in the tropics usually focuses on adverse ecological consequences. Less recognized, but equally important to inhabitants of these affected regions, is an increasing susceptibility to rainfall-induced debris flows and their associated impacts. The same high rainfall rates that sustain tropical forest cover can often serve as the triggering mechanism for debris flows. The natural rate of debris flow occurrence on steep slopes subject to episodic, intense rainfall is dependent on the stabilizing effect of tropical forests. Either loss or significant reduction in forest cover can weaken this natural defense. Information from postdisaster observations and research on the November 1988 storm event in southern Thailand provides a case study illustrating the potential impacts of increased debris flow susceptibility resulting from conversion of forest cover to rubber tree crops. Development resulting in the loss of tropical forest cover may be accompanied by local increase in population, property development, and infrastructure. Consequently, the potentially disastrous consequences of increased debris flow occurrence are amplified by the greater vulnerability of local populations. Preserving the tropical forest cover is an obvious and often difficult means of retaining this natural protection. Effective policy should capitalize on the values of tropical forests as part of the strategy for retaining adequate forest cover. Policy should also seek to avoid creating pressures that foster forest removal or their conversion to other types of land cover in steep terrain. Areas where tropical forests were converted to other cover types can be restored to secondary forests to avoid a permanent state of increased debris flow susceptibility. Restoration of secondary tropical forests can successfully re-establish the forest characteristics that limit debris flow occurrence. Experience in Central America and the Caribbean demonstrates that successful restoration is possible but requires a significant commitment of both time and resources. In addition to the cost and technical difficulties involved, the increased susceptibility to debris flow occurrence persists through many years until successful restoration is achieved. Both retention of existing tropical forests and restoration of forest cover where loss has occurred are often justified by the reduced risk of debris flow impacts to vulnerable populations and infrastructure. © 2012 Springer-Verlag (outside the USA). Source


Mills L.J.,U.S. Environmental Protection Agency | Henderson W.M.,Ecosystems Research Division | Jayaraman S.,U.S. Environmental Protection Agency | Gutjahr-Gobell R.E.,U.S. Environmental Protection Agency | And 3 more authors.
Environmental Toxicology | Year: 2015

Tamoxifen is an endocrine-active pharmaceutical (EAP) that is used world-wide. Because tamoxifen is a ubiquitous pharmaceutical and interacts with estrogen receptors, a case study was conducted with this compound to (1) determine effects on reproductive endpoints in a nontarget species (i.e., a fish), (2) compare biologically-active metabolites across species, (3) assess whether in vitro assays predict in vivo results, and (4) investigate metabolomic profiles in tamoxifen-treated fish to better understand the biological mechanisms of tamoxifen toxicity. In reproductive assays, tamoxifen exposure caused a significant reduction in egg production and significantly increased ovarian aromatase activity in spawning adult cunner fish (Tautogolabrus adspersus). In plasma from tamoxifen-exposed cunner, the predominant metabolite was 4-hydroxytamoxifen, while in rats it was N-desmethyltamoxifen. Because 4-hydroxytamoxifen is a more biologically active metabolite than N-desmethyltamoxifen, this difference could result in a different level of risk for the two species. The results of in vitro assays with fish hepatic microsomes to assess tamoxifen metabolism did not match in vivo results, indicating probable differences in excretion of tamoxifen metabolites in fish compared with rats. For the first time, a complete in vitro characterization of the metabolism of tamoxifen using fish microsomes is presented. Furthermore, a metabolomic investigation of cunner gonad extracts demonstrates that tamoxifen alters the biochemical profile in this nontarget species. Understanding the consequence of tamoxifen exposure in nontarget species, and assessing the discrepancies between sex- and species-mediated endpoints, is a step toward understanding how to accurately assess the risks posed by EAPs, such as tamoxifen, in the aquatic environment. © 2015 Wiley Periodicals, Inc. Source


Ekman D.R.,Ecosystems Research Division | Skelton D.M.,Ecosystems Research Division | Davis J.M.,Ecosystems Research Division | Villeneuve D.L.,US Ecology | And 5 more authors.
Environmental Science and Technology | Year: 2015

The application of 'omics tools to biologically based monitoring and surveillance of aquatic environments shows considerable promise for complementing chemical monitoring in ecological risk assessments. However, few of the current approaches offer the ability to sample ecologically relevant species (e.g., fish) in a way that produces minimal impact on the health of the organism(s) under study. In the current study we employ liquid chromatography tandem mass spectrometry (LC-MS/MS) to assess the potential for skin mucus-based metabolomics for minimally invasive sampling of the fathead minnow (FHM; Pimephales promelas). Using this approach we were able to detect 204 distinct metabolites in the FHM skin mucus metabolome representing a large number of metabolite classes. An analysis of the sex specificity of the skin mucus metabolome showed it to be highly sexually dimorphic with 72 of the detected metabolites showing a statistically significant bias with regard to sex. Finally, in a proof-of-concept fashion we report on the use of skin mucus-based metabolomics to assess exposures in male and female fathead minnows to an environmentally relevant concentration of bisphenol A, a nearly ubiquitous environmental contaminant and an established endocrine active chemical. © 2015 American Chemical Society. Source

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