Organic matter and the geotechnical properties of submarine sediments     

George H. Keller 《Geo-Marine Letters》1982,2(3-4):191-198

Continental slope deposits off Peru and Oregon where coastal upwelling is a pronounced oceanographic process possess significant concentrations of organic carbon. Geotechnical properties are altered to varying degrees by the organic matter. Organic matter absorbs water and causes clay-size particles to aggregate forming an open fabric. This causes unusually high water contents and plasticity and exceptionally low wet bulk densities. Some of these deposits show notable increases in shear strength, sensitivity and degree of apparent overconsolidation. Owing to the unique geotechnical properties, sediment stability characteristics are considered to be poor in situations of excess pore pressures. Failure appears to take the form of a fluidized flow somewhat similar to the quick clays of Scandinavia.  相似文献   

A Comparative Evaluation of the Geotechnical Index Properties of Clayey Sediments along the West Coast of India     

Thomas Mathai  M. Suresh Chandran  S. B. Nair  M. R. Asoka Kumar  Satish Kumar  P. Praveen Kumar  K. N. Rajarama  T. Stephen George 《Marine Georesources & Geotechnology》2007,25(3):151-165

Sediment core samples collected during geotechnical surveys along the West Coast of India in the near shore areas of Arabian Sea have generated data on the geotechnical index properties of clayey sediments up to nearly 5 m depth below seafloor. A comparative study of three sectors within themselves is attempted before carrying out a final evaluation between the sectors. Cohesive clayey sediments of Gujarat sector are comparable though widely variant in a few aspects; in the Maharashtra-Goa-Karnataka sector though, plasticity levels and clay type vary, and activity and consistency levels are quite similar. Though broadly comparable, the clayey sediments of Kerala-Tamilnadu sector have quite diverse characteristics that fail to conform to any particular pattern as each area has an exclusive set of geotechnical properties.  相似文献   

Monitoring coastal northern cod: towards an optimal survey of Smith Sound, Newfoundland   总被引：2，自引：2，他引：2  

Rose  George A 《ICES Journal of Marine Science》2003,60(3):453-462

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Biochemical and ultrastructural observations of long-term silver accumulation in the mussel, Mytilus edulis     

S.G. George  B.J.S. Pirie  A. Calabrese  D.A. Nelson 《Marine environmental research》1986,18(4)

The cellular distribution and chemical forms of Ag were determined in mussels after accumulation of the metal from sea water. The major accumulations were either in the vacuoles of connective tissue macrophages, where it was associated with S, or in deposits in the fibrillar layer of the basement membranes of the digestive diverticulum and kidney epithelia, where it was bound to the sulphydryl and sulphate groups of glycoproteins and proteoglycans. In acutely exposed animals, about 10 % of the accumulated Ag was found in a (Ag, Cu)-binding protein with characteristics indicating that it may be a metallothionein. There was a concomitant increase in the body Cu levels after Ag exposure and 40 % of this was bound to this low molecular weight metal-binding protein.  相似文献   

Density-dependent distribution of demersal juvenile Atlantic cod (Gadus morhua) in Placentia Bay, Newfoundland     

Robichaud  David; Rose  George A. 《ICES Journal of Marine Science》2006,63(4):766-774

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An in vitro procedure for evaluation of early stage oxidative stress in an established fish cell line applied to investigation of PHAH and pesticide toxicity   总被引：1，自引：0，他引：1  

Ruiz-Leal M  George S 《Marine environmental research》2004,58(2-5):631-635

Oxidative stress by increased production of reactive oxygen species such as superoxide has been implicated in the toxicity of PCB's and non-target toxicity of many pesticides. We report the development of a microplate-based method for determination of early stage oxidative stress using an established cell line (EPC) from a skin tumour of carp Cyprinus carpio L. and 2',7'-dichlorodihydrofluorescein diacetate (H(2)-DCFDA) as a fluorescent probe for detection of reactive oxygen species (ROS) formation. Sublethal concentrations of the herbicide Paraquat, an established redox cycling agent and a crude PCB mixture, Arochlor 1254 elicited a linear increase in ROS formation over 2 h exposure which was some 45- and 10-fold higher, respectively, than attributable to basal respiration, confirming the suitability and response of the test system. Whilst in vivo studies in mammals have implicated early stage oxidative stress in the toxicity of pesticides, we did not observe an increase in ROS production after exposure of EPC cells to sublethal concentrations of Carbaryl, 2,4-DDT, Lindane or Malathion implying that this is not the causative mechanism of acute toxicity in this fish cell line. The apparent involvement of oxidative stress in their mammalian toxicity may therefore be an indirect effect or dependent upon compound metabolism.  相似文献   

Using Large-Eddy Simulations to Define Spectral and Coherence Characteristics of the Hurricane Boundary Layer for Wind-Energy Applications     

Rochelle P. Worsnop  George H. Bryan  Julie K. Lundquist  Jun A. Zhang 《Boundary-Layer Meteorology》2017,165(1):55-86

Offshore wind-energy development is planned for regions where hurricanes commonly occur, such as the USA Atlantic Coast. Even the most robust wind-turbine design (IEC Class I) may be unable to withstand a Category-2 hurricane (hub-height wind speeds >50 m s\(^{-1}\)). Characteristics of the hurricane boundary layer that affect the structural integrity of turbines, especially in major hurricanes, are poorly understood, primarily due to a lack of adequate observations that span typical turbine heights (<200 m above sea level). To provide these data, we use large-eddy simulations to produce wind profiles of an idealized Category-5 hurricane at high spatial (10 m) and temporal (0.1 s) resolution. By comparison with unique flight-level observations from a field project, we find that a relatively simple configuration of the Cloud Model I model accurately represents the properties of Hurricane Isabel (2003) in terms of mean wind speeds, wind-speed variances, and power spectra. Comparisons of power spectra and coherence curves derived from our hurricane simulations to those used in current turbine design standards suggest that adjustments to these standards may be needed to capture characteristics of turbulence seen within the simulated hurricane boundary layer. To enable improved design standards for wind turbines to withstand hurricanes, we suggest modifications to account for shifts in peak power to higher frequencies and greater spectral coherence at large separations.  相似文献   

China’s metropolises in transformation: neoliberalizing politics,land commodification,and uneven development in Beijing     

George C. S. Lin  Amy Y. Zhang 《Urban geography》2017,38(5):643-665

ABSTRACT

Existing theory of urban transformation under neoliberalization describes cities as the institutional arena in and through which neoliberal strategies of urbanism emanate and are contested. Emphasis is placed on the interaction between state and market without paying adequate attention to their internal dynamics. This study of urban transformation in the Beijing metropolis identifies a distinct trajectory whereby commodification of urban land has been actively pursued in response to the decentralization of developmental responsibilities and recentralization of tax revenue collection instituted by the central state. An urban development strategy is practiced whereby land commodification, city planning, and mega event hosting are integrated and mutually reinforcing. The research shows a pattern of land commodification and development dominated by newly developed construction land in the near suburbs, and reveals a picture of increased spatial inequality and intensified social discontent as a consequence of city-centered land development. Contrary to popular perception of the state and market as diametrically opposed principles of political organization, the Chinese state is found to have transformed and reshuffled itself to embrace and take advantage of the market for its developmental agenda.  相似文献   

Molecular iodine reduction by natural and model organic substances in seawater     

Victor W. Truesdale  George W. Luther III 《Aquatic Geochemistry》1995,1(1):89-104

The reactivity of 2 µM molecular iodine in seawater toward various organic compounds containing aromatic, -keto, amino, olefinic and sugar functional groups was investigated. More detailed studies have been made of the reduction kinetics with salicylic acid, -ketoglutaric acid and the polypeptide oxidized glutathione, particularly to establish whether variation over the pH range 4–9 would provide a similar reduction reactivity or fingerprint to that of molecular iodine added to natural seawater. The data indicates that compounds with only one functional group react with first order kinetics whereas compounds with multiple functional groups show more complex behaviour. Kinetic and thermodynamic modelling indicates that HOI is the main iodine species reacting with organic matter at seawater pH of 8.2. Based on the pH fingerprints, peptides and compounds containing carbonyl or -keto groups are the key reductants of molecular iodine added to seawater. These compounds form C-I and N-I bonds which can allow for a rich organic iodine chemistry in seawater. The model compound results are discussed in relation to oceanic processes.  相似文献   

Experimental determination of HONO mass accommodation coefficients using two different techniques   总被引：4，自引：0，他引：4  

A. Bongartz  J. Kames  U. Schurath  Ch. George  Ph. Mirabel  J. L. Ponche 《Journal of Atmospheric Chemistry》1994,18(2):149-169

The mass accommodation coefficient _HONO of gaseous nitrous acid on water surfaces has been determined in a cooperation between the Universities of Strasbourg and Bonn. The droplet train technique (Strasbourg) yielded 0.04<_HONO<0.09 for an estimated surface temperature of 245 K, while the liquid jet technique (Bonn) yielded 0.03<_HONO<0.15 for a surface temperature of 297 K. The uncertainty ranges allow for experimental scatter and estimated uncertainties in diffusion coefficients. The same HONO source and analytical equipment were used for both experiments, which were run in parallel. The results indicate that the exchange rate of HONO between atmospheric water droplets and interstitial air is not inhibited by interfacial resistance.  相似文献