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991.
Visualization of a collapsing vertical packet of patches in a laboratory experiment and the results of acoustical sounding under field conditions allowed us to discriminate the stage of its evolution which was previously unknown. It is defined by the variations of the horizontal dimensions of patches and their effective scattering surface with a period ofT=150–250/N, whereN is the Brunt-Väisälä frequency. The horizontal dimensions of patches can reach 40% of their final dimensions at the evolution stage discriminated.Translated by Mikhail M. Trufanov. 相似文献
992.
Adriano Mazzini D. Duranti R. Jonk J. Parnell B. T. Cronin A. Hurst M. Quine 《Geo-Marine Letters》2003,23(3-4):323-339
Petrographic and geochemical analyses performed on a North Sea core from the Gryphon Field reveal the presence of palaeo-degassing features surrounded by injected sandstones in the Eocene interval. The injected sandstones are oil-stained and poorly cemented by carbonate and quartz. 18O isotope analyses indicate that carbonate cementation occurred during shallow burial (likely less than about 300 m). Depleted 13C (around –30 V-PDB) carbonate cement suggests that bicarbonate was derived from the microbial oxidation of oil and gas. Late quartz overgrowths enclose oil present in the injected units. The tubular degassing conduits are composed of zoned cements and have 18O and 13C isotope values similar to the injected sandstones, indicating that oil and gas seepage induced the precipitation of authigenic carbonate in the shallow subsurface. Oil inclusions in inter- and intra-crystal cement sites in both injected sandstones and degassing conduits indicate that oil seepage was an ongoing feature at shallow burial. A proposed model involves oil and gas seepage and the formation of the degassing conduits, followed by a sand injection phase. It seems likely that oil and gas continued to leak towards the seabed by exploiting the network of permeable injected sandstones and the horizons of porous degassing features. 相似文献
993.
V. A. Frol’kis I. L. Karol’ A. A. Kiselev Yu. E. Ozolin V. A. Zubov 《Izvestiya Atmospheric and Oceanic Physics》2007,43(4):413-422
This is a study of the sensitivity of model results (atmospheric content of main gas constituents and radiative characteristics of the atmosphere) to errors in emissions of a number of atmospheric gaseous pollutants. Groups of the model variables most dependent on these errors are selected. Two variants of emissions are considered: one without their evolution and the other with their variation according to the IPCC scenario. The estimates are made on the basis of standard statistical methods for the results obtained with the detailed onedimensional radiative—photochemical model of the Main Geophysical Observatory (MGO). Some approaches to such estimations with models of higher complexity and to the solution of the inverse problem (i.e., the estimation of the necessary accuracy of external model parameters for obtaining the given accuracy of model results) are outlined. 相似文献
994.
Mud and fluid migration in active mud volcanoes in Azerbaijan 总被引:7,自引:2,他引:7
Mud volcanic eruptions in Azerbaijan normally last for less than a few hours, and are characterized by vigorous extrusion of mud breccias, hydrocarbon gases, and waters. Recent fieldwork and mapping on four active mud volcanoes show that dormant period activity ranges from quiet to vigorous flow of mud and fluids. Geochemical analyses of expelled waters show a wide range in solute concentrations, suggesting the existence of a complex plumbing system. The mud and fluids have a deep origin, but are sometimes stored in intermediate-depth mud chambers. A mixing model between deep-seated saline waters and shallow meteoric water is proposed. 相似文献
995.
Hydrodynamic and sediment transport measurements from instrumentation deployed during a 54-day winter period at two sites on the Louisiana inner shelf are presented. Strong extratropical storms, with wind speeds of 7.8 to 15.1 m s-1, were the dominant forcing mechanism during the study. These typically caused mean oscillatory flows and shear velocities about 33% higher than fair weather (averaging 12.3 and 3.2 cm s-1 at the landward site, and 11.4 and 2.7 cm s-1 at the seaward site, respectively). These responses were coupled with mean near-bottom currents more than twice as strong as during fair weather (10.3 and 7.5 cm s-1 at the landward and seaward sites, respectively). These flowed in approximately the same direction as the veering wind, causing a net offshore transport of fine sand. Weak storms were responsible for little sediment transport whereas during fair weather, onshore sand transport of approximately 25-75% of the storm values appears to have occurred. This contradicts previous predictions of negligible fair-weather sediment movement on this inner shelf. 相似文献
996.
M.E. vinogradov E.A. Shushkina V.I. Vedernikov N.P. Nezlin V.I. Gagarin 《Deep Sea Research Part II: Topical Studies in Oceanography》1997,44(9-10)
Data collected from 20 years of observations by the P. P. Shirshov Institute of Oceanology (about 250 comprehensive ecosystem stations) are summarized to evaluate the primary production and biomass of the principal groups of plankton in the Pacific Ocean. The stations were classified into geographical regions according to satellite determined criteria. The areas of these regions were evaluated according to CZCS data from 1978 to 1986. The total value of primary production was evaluated as 26·9 Gt C year−1. Taking the “bottle effect” correction into account, this value may be as high as 45.6 Gt C year−1. Total biomass values of phytoplankton (134 Mt C), bacteria (86 Mt C), protozoa (26 Mt C) and mesoplankton (184 Mt C) were also calculated. Seasonal variabilities of all these values were remarkably insignificant. 相似文献
997.
Water velocity and density profiles were obtained in late-spring and late-winter to document reversing mean circulation patterns at the entrance to a semiarid coastal lagoon, the Bay of Guaymas, in the Gulf of California, Mexico. The lagoon is shallow but the bathymetry at its entrance is similar to that of temperate estuaries with an asymmetrically positioned channel flanked by shoals. In late-spring the mean circulation at the entrance to the lagoon was driven by horizontal density gradients that arose from excess evaporation over precipitation in the area as evidenced by water density profiles. The lagoon exported relatively warm (25·8 °C) and salty (36·2) water to the Gulf of California through the channel. This export was consistent with inverse estuarine circulation influenced by bathymetry. In late-winter, the circulation at the entrance of the lagoon was mostly driven by wind stress that blew from the northwest, roughly along the main axis of the lagoon. Relatively cool (16·0) °C) and less salty (35·1) water from the Gulf of California was driven into the lagoon within the channel. Density gradients inside the lagoon seem to have played a secondary role in driving the circulation. The late-winter circulation was then estuarine-like, with outflow in the direction of the wind over the shallow areas and a compensatory inflow appearing in the channel as expected from theory of wind-driven flow over bathymetry. This estuarine-like circulation developed despite the lack of measurable freshwater input to the lagoon and was the opposite to that observed in late-spring. These observations then document a reversal in water exchange patterns from season to season in a semiarid coastal lagoon. The observations also constitute one of the few reported examples of flow over shoals driven in the same direction as the wind stress with a compensatory flow in the channel. 相似文献
998.
The stresses generated in the interlock T-junction piles of steel cellular structures used as quays are analysed based on a full scale experimental recording of the stresses in the piles at all stages of construction. Special emphasis is placed on the resonant response of the pile to vibrations of the fill in the interlock cell. Means of stiffening the interlock piles are discussed. A model for the statical behaviour of the interlock pile is postulated and an alternative design for cellular quay construction based on its three-dimensional behaviour rather than the equivalent breadth concept is put forward. This work was instigated by the collapse of three interlock piles during the construction of the deep water quays at Umm Said Port in Qatar. 相似文献
999.
Analysis of microbiological and chitinase activities relative to the white shrimpPenaeus setiferus, and its chitinoclastic endosymbionts, have demonstrated the relevance of total chitinolytic processes in penaeid biology. Microorganisms may serve as a direct source of nutrients for the animal as well as in the elaboration of extracellularin situ chitinase enzymes. The enzyme produced by the predominant gut bacteria,Beneckea neptuna, is a moderately actively inducible chitinase while the shrimp has an indigenous constitutive chitinase and chitobiase system. Factors of temperature, pH, ion inhibition and reducing sugar ratios have been compared for the bacterial and animal enzymes. This dual enzyme system suggests that metabolic chitin transformation may play a vital role in crustacean metabolism. 相似文献
1000.
Core 7710, recovered on the George Bligh/Rockall Channel, is composed of fine grained ocher-colored sediments rich in ferriferous smectite (montmorillonite, beidellite). These sediments were deposited during early Eocene in a shallow marine environment. Their mineralogic, chemical and isotopic constituents indicate subaerial weathering of lower Eocene intermediate igneous rocks (ferrodiorite, marscoiite) eroded from the still-emergent George Bligh and Rockall Banks. Lack of any post Eocene Sediments may be due to major morphologic and hydrologic changes forming sedimentation gaps. 相似文献