Temporal evolution of neutral,thermospheric winds and plasma response using PFISR measurements of gravity waves     

Sharon L. Vadas  Michael J. Nicolls 《Journal of Atmospheric and Solar》2009,71(6-7):744-770

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A laboratory study on the kinetics of the formation of oil-suspended particulate matter aggregates using the NIST-1941b sediment     

Juan Sun  Ali Khelifa  Zhendi Wang  Sharon Wong  Benjamin Fieldhouse 《Marine pollution bulletin》2010,60(10):1701-1707

The formation of oil-suspended particulate matter aggregates (OSAs) results from the heteroaggregation between dispersed oil droplets and suspended particulate matter present in coastal waters. This process has been recognized by the oil spill remediation community to enhance natural cleansing of oiled shorelines and oil dispersion in the water column. While several studies have been conducted on the formation and characteristics of OSAs, few studies have addressed the kinetics of OSA formation. Operationally, this has left decision-makers lacking information on the time scale of this process and its significance to oil dispersion in real spills. A laboratory study was conducted to investigate the kinetics of OSA formation as a function of mixing energy and the sediment-to-oil ratio using the standard reference material 1941b. Results showed that formation of OSAs increased exponentially with the mixing time and reached a maximum within 4 h. When the shaking rate increased from 2.0 to 2.3 Hz, the maximum oil trapping efficiency increased from 20% to 42% and the required shaking time decreased from 3.7 to 0.7 h.  相似文献   

Field validation of antioxidant enzyme biomarkers in mussels (Perna viridis) and clams (Ruditapes philippinarum) transplanted in Hong Kong coastal waters   总被引：4，自引：0，他引：4  

De Luca-Abbott SB  Richardson BJ  McClellan KE  Zheng GJ  Martin M  Lam PK 《Marine pollution bulletin》2005,51(8-12):694-707

Green-lipped mussels, Perna viridis, and Manila clams, Ruditapes philippinarum were sourced from “clean” sites in the Hong Kong region, depurated in a laboratory using uncontaminated filtered seawater for 8 days, and transplanted to a suspected gradient of chemically polluted sites in Hong Kong. After 14- and 28-days of field exposure, several antioxidant parameters including glutathione S transferase (GST), catalase (CAT), glutathione peroxidase (GPx), and glutathione (GSH) were quantified in gill and hepatopancreas tissues. Whole body tissue concentrations of polycyclic aromatic hydrocarbons (PAHs), petroleum hydrocarbons (PHCs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCs) were determined in pooled site samples. Chemical analyses indicated that: (a) clams had higher levels of PAHs, PHCs, DDTs and PCBs, whereas mussels had higher hexachlorocyclohexane (HCHs) and there was no difference between species for dieldrin and remaining OCs; (b) Kat O should not be continued as a “clean” reference site for Hong Kong, because of the levels of contaminants measured and (c) PAH concentrations in the current survey were similar to those previously measured. Toxicological conclusions were: (a) antioxidant responses were different between species; (b) CAT and GST have highest utility in clams for field use in Hong Kong, whereas CAT in both gill and hepatopancreas tissue showed most potential in mussels; (c) significant induction of antioxidant responses over day 0 (excluding GPx in both tissues, and GST in mussel hepatic tissue); (d) groups of contaminants do not consistently induce antioxidant responses and (e) organochlorines and PCBs correlated significantly with CAT and GST in clam hepatopancreas and with CAT in mussel gill and hepatic tissue. Multivariate statistical techniques indicated little relationship between the site patterns for antioxidant responses and the contaminant gradients identified in body burden analysis.  相似文献   

The S-type Ladybird leucogranite suite of southeastern British Columbia: Geochemical and isotopic evidence for a genetic link with migmatite formation in the North American basement gneisses of the Monashee complex   总被引：1，自引：0，他引：1  

Alana M. Hinchey  Sharon D. Carr   《Lithos》2006,90(3-4):223-248

The 62–52 Ma Ladybird granite (LBG) suite is a peraluminous, leucocratic, S-type, quartz monzonitic to granitic suite which occurs as batholiths, stocks, dikes, sills, and pegmatite veins predominantly in the high-grade rocks of the Shuswap complex, in southeastern British Columbia. The emplacement of the LBG was synchronous with the production of abundant migmatites within Thor–Odin dome of the Monashee complex, an exposure of North American basement, exhumed from depths of ca. 26–33 km by Eocene extensional faults. The LBG and the leucosome in migmatites from Thor–Odin dome have similar major and trace element patterns, and are both characterized by zircons which have inherited Precambrian cores. Whole rock Nd isotope compositions show a range of values for the LBG with εNd_{(55 Ma)} values from − 5.0 to − 17.2. The εNd_{(55 Ma)} for the leucosome samples range from − 9.5 to − 23.6, overlapping with those of the granitic suite. These data support the interpretation of a genetic link between formation of the LBG suite and melting of North American basement rocks, such as those exposed in the core of Thor–Odin dome. The leucosome samples have lower high field strength element (HFSE) concentrations and positive Eu anomalies, whereas the LBG samples have higher HFSE concentrations and negative Eu anomalies. The similar trace element characteristics suggest that the leucosome from the migmatites and the LBG are related, whereby most of the leucosome samples are cumulates and the LBG samples represent evolved or residual melts. The initial ⁸⁷Sr/⁸⁶Sr isotope values for both the LBG and leucosome samples have a large range. However, the initial Sr isotopic ratios for the LBG suite are lower than those of the leucosome samples, with ⁸⁷Sr/⁸⁶Sr_{(55 Ma)} ranging from 0.70603 to 0.73688 and 0.74256 to 0.76593, respectively. This isotopic discrepancy suggests either: a) isotopic disequilibrium during partial melting in the mid- to lower crust where the leucosome formed, b) the distribution of Sr during partial melting was controlled by different melt-producing reactions, and/or c) isotopic heterogeneity in the source rocks. At least part of the LBG suite likely formed via melting of North American basement rocks that were dominantly of sedimentary origin. Melting of the Proterozoic supracrustal metasedimentary rocks overlying North American basement may also have contributed to the formation of the different phases of the suite found at the regional scale. However, the abundant leucosomes in the basement rocks of Thor–Odin dome may mark the paths along which anatectic melt migrated in the structurally overlying Ladybird granites of the South Fosthall pluton.  相似文献   

Shear modulus, heat capacity, viscosity and structural relaxation time of Na2O–Al2O3–SiO2 and Na2O–Fe2O3–Al2O3–SiO2 melts     

Katarzyna Falenty  Sharon L. Webb 《Physics and Chemistry of Minerals》2010,37(9):613-634

The configurational heat capacity, shear modulus and shear viscosity of a series of Na₂O–Fe₂O₃–Al₂O₃–SiO₂ melts have been determined as a function of composition. A change in composition dependence of each of the physical properties is observed as Na₂O/(Na₂O + Al₂O₃) is decreased, and the peralkaline melts become peraluminous and a new charge-balanced Al-structure appears in the melts. Of special interest are the frequency dependent (1 mHz–1 Hz) measurements of the shear modulus. These forced oscillation measurements determine the lifetimes of Si–O bonds and Na–O bonds in the melt. The lifetime of the Al–O bonds could not, however, be resolved from the mechanical spectrum. Therefore, it appears that the lifetime of Al–O bonds in these melts is similar to that of Si–O bonds with the Al–O relaxation peak being subsumed by the Si–O relaxation peak. The appearance of a new Al-structure in the peraluminous melts also cannot be resolved from the mechanical spectra, although a change in elastic shear modulus is determined as a function of composition. The structural shear-relaxation time of some of these melts is not that which is predicted by the Maxwell equation, but up to 1.5 orders of magnitude faster. Although the configurational heat capacity, density and shear modulus of the melts show a change in trend as a function of composition at the boundary between peralkaline and peraluminous, the deviation in relaxation time from the Maxwell equation occurs in the peralkaline regime. The measured relaxation times for both the very peralkaline melts and the peraluminous melts are identical with the calculated Maxwell relaxation time. As the Maxwell equation was created to describe the timescale of flow of a mono-structure material, a deviation from the prediction would indicate that the structure of the melt is too complex to be described by this simple flow equation. One possibility is that Al-rich channels form and then disappear with decreasing Si/Al, and that the flow is dominated by the lifetime of Si–O bonds in the Al-poor peralkaline melts, and by the lifetime of Al–O bonds in the relatively Si-poor peralkaline and peraluminous melts with a complex flow mechanism occurring in the mid-compositions. This anomalous deviation from the calculated relaxation time appears to be independent of the change in structure expected to occur at the peralkaline/peraluminous boundary due to the lack of charge-balancing cations for the Al-tetrahedra.  相似文献   

Evaluating the Science-Policy Interface for Climate Change Research     

Sharon A. Jones  Baruch Fischhoff  Denise Lach 《Climatic change》1999,43(3):581-599

We propose a general method for evaluating, and possibly improving, the interface between scientific research and policy-making institutions. The method considers the adequacy of both institutional structures for incorporating research, and research for addressing institutional needs. It involves both interviews (with policy makers and scientists) and formal analyses of the links between the research and the decisions described in the interviews. A case study applies the method in analyzing the usefulness of climate change research for managing salmon runs in the Pacific Northwest. It shows these policy makers to be receptive to the research, which is, in principle, relevant to them. However, they are unable to use it because the research is not currently formulated in ways compatible with current decision-making models. For their part, these models are not comprehensive enough to capture the full range of potentially relevant environmental forcers, including climate change.  相似文献   

A high magnitude storm and flood in a hyperarid catchment,Nahal Zin,Negev Desert,Israel     

Noam Greenbaum  Adina Margalit  Asher P. Schick  David Sharon  Victor R. Baker 《水文研究》1998,12(1):1-23

In October 1991 a high magnitude rainstorm flood, estimated return period 40 years, occurred in Nahal Zin, a 1400 km² catchment in the hyperarid Negev Desert. The meso-scale structure of the storm was a curved squall line that developed from a thunderstorm in accordance with the topography of the catchment divide, by which it was strongly affected. Tropical moisture reached the area via the subtropical jet stream, in conjunction with a lower level northward intrusion of the Red Sea trough (RST-N) into the Mediterranean Sea. Rainfall, as measured at the few and sparse gauging stations, was much too small to account for the resulting large flood. Peak flow and other hydraulic characteristics of the flood were indirectly reconstructed. The techniques of palaeoflood hydrology used were based on sedimentological evidence of fine-grained flood sediments deposited in back-flooded tributaries, as well as on other stage indicators. The HEC-2 procedure was employed to determine water surface profiles. The spatial and temporal characteristics of the event were studied through a combination of rainstorm analysis, remote sensing, hydrological and sedimentological data; they jointly explain the magnitude and timing of tributary contributions producing the integrated flood in the main channel. The flood as reconstructed reveals a three-peak hydrograph: two peaks were generated by the same storm but had different floodwave arrival times in the main channel; the third resulted from a local rainstorm which occurred on the following day and covered only one tributary. The curved structure of the storm and its dynamics in relation to catchment orientation resulted in storm move- ment in tandem with the floodwave. The synchronous contribution from all main tributaries preserved evidence of the floodwave both in stage and volume by replacing the transmission losses in the sections with thick alluvium. Other high magnitude floods on record for the large Negev Desert catchments are caused by a cold upper air incursion associated with the RST-N. Most of them occur in the autumn and are caused by storms with high-intensity rainfall. This is in stark contrast with the flooding behaviour of the semi-arid zone further north, which is linked primarily to the core of the Mediterranean winter. The complexities involved in the generation of a large desert flood, as revealed by this study, illustrate the fallacy of applying routine hydrological modelling to such events, and underline the need to study the processes involved in adequate detail. © 1998 John Wiley & Sons, Ltd.  相似文献   

Earthquake Response of Ring Foundation in Cohesionless Soil     

Birid  Kedar  Choudhury  Deepankar 《Geotechnical and Geological Engineering》2022,40(8):4269-4288

Geotechnical and Geological Engineering - Ring foundations are commonly adopted to support tall and heavy cylindrical structures such as silos, chimneys, cooling towers, circular storage tanks, and...  相似文献