The QuakeSim Project: Web Services for Managing Geophysical Data and Applications     

Marlon E. Pierce  Geoffrey C. Fox  Mehmet S. Aktas  Galip Aydin  Harshawardhan Gadgil  Zhigang Qi  Ahmet Sayar 《Pure and Applied Geophysics》2008,165(3-4):635-651

We describe our distributed systems research efforts to build the “cyberinfrastructure” components that constitute a geophysical Grid, or more accurately, a Grid of Grids. Service-oriented computing principles are used to build a distributed infrastructure of Web accessible components for accessing data and scientific applications. Our data services fall into two major categories: Archival, database-backed services based around Geographical Information System (GIS) standards from the Open Geospatial Consortium, and streaming services that can be used to filter and route real-time data sources such as Global Positioning System data streams. Execution support services include application execution management services and services for transferring remote files. These data and execution service families are bound together through metadata information and workflow services for service orchestration. Users may access the system through the QuakeSim scientific Web portal, which is built using a portlet component approach.  相似文献   

Period–luminosity relations for red supergiant variables – II. The distance to M101     

J. S. Jurcevic  M. J. Pierce  G. H. Jacoby 《Monthly notices of the Royal Astronomical Society》2000,313(4):868-880

We report the discovery of 42 red supergiant variables (RSVs) in the late-type spiral galaxy M101. Periods for the luminosity variation of these RSVs were determined from 20 epochs of ground-based CCD photometry in the Kron–Cousins R band obtained with the KPNO 2.1-m and WIYN 3.5-m telescopes over a span of three years. The periods found were in the range 200–1300 days. Using the relationship between the RSV periods and their luminosity in the Kron–Cousins I band, we estimate a reddening-corrected distance modulus to M101 of 29.40±0.16 mag (based on a distance modulus of 18.5±0.1 mag for the Large Magellanic Cloud). This distance is consistent with the Hubble Space Telescope Key Project Cepheid distances of 29.34±0.17 mag for the outer field of M101 and 29.21±0.17 mag for the inner field.  相似文献   

Brevetoxin abundance and composition during ECOHAB-Florida field monitoring cruises in the Gulf of Mexico     

Richard Pierce  Michael Henry  Patricia Blum 《Continental Shelf Research》2008

This project was undertaken to provide information about the composition and fate of brevetoxins in concert with the multidisciplinary study, ECOHAB-FL, of Karenia brevis blooms in the Gulf of Mexico. Brevetoxin composition was provided for water samples collected during and in the absence of K. brevis blooms from November 1998, through September 2002. The identity and concentration of the most abundant brevetoxins were determined using high performance liquid chromatography with ultraviolet diode array detection (HPLC-DAD). The analytical methods changed in 2002 to the use of a mass spectrometer for brevetoxin identification and quantitation. The most abundant brevetoxins observed during blooms were PbTx-1, -2 and -3. PbTx-2 was the most abundant toxin observed in viable bloom situations with an abundance of K. brevis cells. Starting with the 2000 cruises, a distinction was made between intra-cellular toxins (inside viable K. brevis cells) and extra-cellular brevetoxins (dissolved brevetoxins outside of the cell). An important observation was the change in composition of the major brevetoxins from intra-cellular to extra-cellular toxins. The most abundant intra-cellular toxin was PbTx-2, whereas the most abundant brevetoxin recovered from the extra-cellular (dissolved) fraction in the water was PbTx-3. The abundance of PbTx-3 relative to PbTx-2 generally increased as a bloom aged, indicating the conversion of PbTx-2 to -3 as cells lysed, and the persistence of PbTx-3 in the water after cell death.  相似文献   

Allogenic and autogenic effects on mangrove dynamics from the Ceará Mirim River,north‐eastern Brazil,during the middle and late Holocene          下载免费PDF全文

Samuel Rodrigues Ribeiro  Edson José Louzada Batista  Marcelo C.L. Cohen  Marlon Carlos França  Luiz C.R. Pessenda  Neuza A. Fontes  Igor C.C. Alves  José A. Bendassolli 《地球表面变化过程与地形》2018,43(8):1622-1635

It is possible that climate changes and sea level fluctuations (allogenic processes) are and will cause major changes in mangrove dynamics. However, other driving forces may be significantly affecting this system. Distinguishing allogenic and autogenic influence on mangroves is a challenging question, because mechanisms related to the natural dynamics of depositional environments (autogenic processes) have strong influences on the establishment and degradation of mangroves. Thus, impacts on mangroves caused by autogenic processes may be erroneously attributed to allogenic mechanisms. Therefore, it is imperative to identify the ‘fingerprint’ of global changes in modern mangrove dynamics. In order to characterize the influence of these forces on mangroves, this work has used geomorphology and vegetation maps integrated with sedimentological and palynological data, radiocarbon dating, as well as δ¹³C, δ¹⁵N and C/N from sedimentary organic matter. The inter‐proxy analyses reveal an estuarine influence with mangrove development along the Ceará Mirim River, north‐eastern Brazil, since ~6920 cal yr bp , after the post‐glacial sea level rise. Relative sea level (RSL) has been stable during the middle and late Holocene. Mangrove establishment along this fluvial valley begins at about 6920 cal yr bp , caused by the sea‐level stabilization, an allogenic influence. However, after its establishment, wetland dynamics were mainly controlled by autogenic factors, related to channel migrations, instead of allogenic process. Some influence of sea‐level and climate changes on mangrove dynamics in this estuarine channel have been weakened by more intense tidal channels activities. Therefore, the expansion and contraction of mangrove areas along the estuary of the Ceará Mirim River since 6920 cal yr bp has been mainly influenced by channel dynamics that regulate the accretion and erosion of mangrove substrates. Copyright © 2018 John Wiley & Sons, Ltd.  相似文献   

Geosynthesis of dibenzothiophene and alkyl dibenzothiophenes in crude oils and sediments by carbon catalysis     

Muhammad Asif  Robert Alexander  Tahira Fazeelat  Kieran Pierce 《Organic Geochemistry》2009,40(8):895-901

Sediment extracts and crude oils have been shown to contain methyl substituted biphenyls and dibenzothiophenes, with isomer distributions suggesting a geochemical relationship between the two compound classes. Laboratory simulation experiments have shown that carbon catalyses the reaction between surface adsorbed sulfur and biphenyl to form dibenzothiophene. Similarly, the methyl substituted biphenyls reacted to yield corresponding methyl dibenzothiophenes. We suggest that the widespread distribution of dibenzothiophene and alkylated dibenzothiophenes in sediments and crude oils is the result of a catalytic reaction of biphenyl ring systems and surface-adsorbed sulfur on the surface of carbonaceous material.  相似文献   

Formation and reactions of alkyl adamantanes in sediments: Carbon surface reactions     

Lyndon BerwickRobert Alexander  Kieran Pierce 《Organic Geochemistry》2011,42(7):752-761

Diamondoids are hydrocarbons with a carbon skeleton that is superimposable on the diamond lattice. Adamantane is the cage-shaped primary unit of diamondoids and occurs widely in sediments and petroleum. The first report of adamantane isolated from petroleum extends back seven decades, but the precursors and reaction mechanisms for the formation of adamantane and related diamondoids in sediments has remained unclear. We report the formation of alkyl adamantanes by heating β-ionone with activated carbon in closed system pyrolysis experiments in the range 170-320 °C. In addition, hydrogen exchange, demethylation, methyl transfer and isomerisation reactions were observed when the model compounds adamantane and 1,3-dimethyladamantane were heated at moderate temperature with activated carbon. A reaction pathway for the formation and reactions of alkyl adamantanes is proposed on the basis of ring isomerisation of adamantane to protoadamantane on the activated carbon surface. The carbonaceous surface reactions described help account for the occurrence and distribution of alkyl adamantanes in petroleum basins, as evidenced by the strong linear relationships between compound pairs related by isomerisation and demethylation for a set of crude oils from the Carnarvon Basin, Western Australia.  相似文献   

Cone Penetrometer Testing and Discrete-Depth Ground Water SamplingL Techniques: A Cost-Effective Method of Site Characterization in a Multiple-Aquifer Setting     

Dawn A. Zemo  Yvonne G. Pierce  John D. Gallinatti 《Ground Water Monitoring & Remediation》1994,14(4):176-182

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The right to move: informal use rights and urban practices of mobility     

Joseph Pierce  Mary Lawhon 《Urban geography》2018,39(5):667-686

Everyday urban practices are enabled by both formal and informal rights regimes. Researchers often focus on the effects of formal rights; informal rights to use urban spaces have been less widely examined, particularly in North America. This article examines practices of intra-urban mobility in a gentrifying area of Portland, Oregon. We find that rights regimes regarding movement in urban space importantly shape who uses particular transit strategies and infrastructures. Specifically, we identify rights regimes rooted in explications of a city ideal and a neighborhood ethic. We suggest that Portland’s widely admired transit planning process has not sufficiently engaged with informal use rights in transit spaces, leading to uneven adoption of a transportation infrastructure that re-inscribes historic racialized injustices. An examination of informal use rights complicates common rights analytics, including those leveraging Lefebvre’s right to the city, emphasizing how all urban rights are contingent, contested and negotiated.  相似文献   

Experimentally determined dissolution kinetics of Na-rich borosilicate glass at far from equilibrium conditions: Implications for Transition State Theory     

Jonathan P. Icenhower  B. Peter McGrail  Eric M. Pierce  David K. Shuh  Jackie L. Steele 《Geochimica et cosmochimica acta》2008,72(12):2767-2788

The dissolution kinetics of five chemically complex and five chemically simple sodium silicate glass compositions (Na-Si±Al±B) were determined over a range of solution saturation values by varying the flow-through rates (1-100 mL/d) in a dynamic single-pass flow-through (SPFT) apparatus. The chemically complex borosilicate glasses are representative of prospective hosts for radioactive waste disposal and are characterized by relatively high molar Si/(Si + Al) and Na/(Al + B) ratios (>0.7 and >1.0, respectively). Analysis by X-ray absorption spectroscopy (XAS) indicates that the fraction of ^ivB to ⁱⁱⁱB (N₄) varies from 0.66 to 0.70. Despite large differences in bulk chemistry, values of δ²⁹Si peak shift determined by MAS-NMR varies only by about 7 ppm (δ²⁹Si = −94 to −87 ppm), indicating small differences in polymerization state for the glasses. Forward rates of reaction measured in dynamic experiments converge (average log₁₀ rate [40 °C, pH 9] = −1.87 ± 0.79 [g/(m² d)]) at high values of flow-rate (q) to sample surface area (S). Dissolution rates are independent of total Free Energy of Hydration (FEH) and this model appears to overestimate the impact of excess Na on chemical durability. For borosilicate glass compositions in which molar Na > Al + B, further addition of Na appears to stabilize the glass structure with respect to hydrolysis and dissolution. Compared to other borosilicate and aluminosilicate glasses, the glass specimens from this study dissolve at nearly the same rate (0-∼56×) as the more polymerized glasses, such as vitreous reedmergnerite (NaBSi₃O₈), albite, and silica. Dissolution of glass follows the order: boroaluminosilicate glass > vitreous reedmergnerite > vitreous albite > silica glass, which is roughly the same order of increasingly negative ²⁹Si chemical shifts. The chemical shift of ²⁹Si is a measure of the extent of bond overlap between Si and O and correlates with the forward rate of reaction. Thus, dissolution appears to be rate-limited by rupture of the Si-O bond, which is consistent with the tenants of Transition State Theory (TST). Therefore, dissolution at far from equilibrium conditions is dependent upon the speed of the rate-controlling elementary reaction and not on the sum of the free energies of hydration of the constituents of boroaluminosilicate glass.  相似文献   

Holocene fire occurrence and alluvial responses at the leading edge of pinyon–juniper migration in the Northern Great Basin,USA     

Kerrie N. Weppner  Jennifer L. Pierce  Julio L. Betancourt 《Quaternary Research》2013

Fire and vegetation records at the City of Rocks National Reserve (CIRO), south-central Idaho, display the interaction of changing climate, fire and vegetation along the migrating front of single-leaf pinyon (Pinus monophylla) and Utah juniper (Juniperus osteosperma). Radiocarbon dating of alluvial charcoal reconstructed local fire occurrence and geomorphic response, and fossil woodrat (Neotoma) middens revealed pinyon and juniper arrivals. Fire peaks occurred ~ 10,700–9500, 7200–6700, 2400–2000, 850–700, and 550–400 cal yr BP, whereas ~ 9500–7200, 6700–4700 and ~ 1500–1000 cal yr BP are fire-free. Wetter climates and denser vegetation fueled episodic fires and debris flows during the early and late Holocene, whereas drier climates and reduced vegetation caused frequent sheetflooding during the mid-Holocene. Increased fires during the wetter and more variable late Holocene suggest variable climate and adequate fuels augment fires at CIRO. Utah juniper and single-leaf pinyon colonized CIRO by 3800 and 2800 cal yr BP, respectively, though pinyon did not expand broadly until ~ 700 cal yr BP. Increased fire-related deposition coincided with regional droughts and pinyon infilling ~ 850–700 and 550–400 cal yr BP. Early and late Holocene vegetation change probably played a major role in accelerated fire activity, which may be sustained into the future due to pinyon–juniper densification and cheatgrass invasion.  相似文献